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Copyright 2001 by the MassachusettsInstitute of Technology and YaleUniversity

Volume 4, Number 4

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Journal of Indust rial Ecology 13

Keywords

environmental technology Factor X IPAT equationmaster equation

technologica l change technologica l optimism

Summary

In the early 1970s Ehrlich and Holdren devised a simpleequation in dialogue with Commoner identifying three fac-

tors that created environmental impact. Thus, impact ( I)was expressed as the product of (1) population, ( P); (2) af-fluence, ( A); and (3) technology, ( T ). This ar ticle tracks thevarious forms the IPAT equation has taken over 30 years

as a means of examining an underlying shift among many environmentalists toward a more accepting view of therole technology can play in sustainable development. Al-

though the IPAT equation was once used to determinewhich single variable was the most damaging to the envi-ronment, an industrial ecology view reverses this usage,recognizing that increases in population and affluence can,in many cases, be balanced by improvements to the envi-ronment offered by technological systems.

The IPAT Equationand Its VariantsChanging Views of Technologyand Environmental Impact

Marian R. ChertowSchool of Forestry and Environmental StudiesYale University

New Haven, CT USA

Address correspondence to:Marian R. Chertow

Yale School of Forestry & EnvironmentalStudies205 Prospect Street

New Haven, CT 06511-2189 [email protected]/forestry/popup/faculty/

chertow.html

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14 Journal of Industr ial Ecology

Introduction

In a provocative article, Rockefeller Universityresearcher Jesse Ausubel asks: Can technologyspare the earth? (Ausubel 1996a). It is a modernrendering of an epochal question concerning therelationship of humanity and nature, and, espe-cially since Malthus and Darwin, of the effect of human population on resources. Surely, technologydoes not offer, on its own, the answer to environ-mental problems. Sustainability is inextricablylinked with economic and social considerationsthat differ across cultures. This article, however,discusses the imperative of technological changeand the role it can play in human and environmen-tal improvement, particularly in the United States.

The vehicle used to begin the discussion of technological change, though phrased math-ematically, is largely a conceptual expression of what factors create environmental impact in thefirst place. This equation represents environ-mental impact, ( I), as the product of three vari-ables, (1) population, ( P); (2) affluence, ( A);and (3) technology, ( T ). The IPAT equationand related formulas were born, along with themodern environmental movement, circa 1970.Although first used to quantify contributions to

unsustainability, the formulation has been rein-terpreted to assess the most promising path tosustainability. This revisionism can be seen aspart of an underlying shift among many environ-mentalists in their attitudes toward technology.This article examines the conversion of theIPAT equation from a contest over which vari-able was worst for the planet to an expression of the profound importance of technological devel-opment in Earths environmental future.

A Historical Perspective

In many ways, the modern environmentalmovement itself was a reaction to unbridled faithin technology, especially over the last 50 years.On the one hand, contemporary researchers con-verge around World War II as the starting point of a generation of unprecedented technological de-velopment springing from governmental policiessupporting scientific advance (Brooks 1987; Free-man 1982; Smith 1990; Spiegel-Rosing and Price

1977). On the other hand, the result of this devel-opment was a quantum leap in environmental im-pact. Prior to World War II, smoke, sewage, andsoot were the main environmental concerns(Heaton et al. 1991, 5). In 1972, the revolution-ary thinker Barry Commoner opined: MostUnited States pollution problems are of relativelyrecent origin. The postwar period, 194546, is aconvenient benchmark, for a number of pollut-antsman-made radioisotopes, detergents, plas-tics, synthetic pesticides, and herbicidesare dueto the emergence, after the war, of new productivetechnologies (1972a, 345).

Commoner conclusively assigned blame, as-

serting that his evidence leads to the generalconclusion that in most of the technological dis-placements which have accompanied thegrowth of the United States economy since1946, the new technology has an appreciablygreater environmental impact than the technol-ogy which it has displaced; and the postwartechnological transformation of productive ac-tivities is the chief reason for the present envi-ronmental crisis (1972a, 349).

Commoners contemporaries, eminent envi-ronmentalists Paul Ehrlich and John Holdren,writing in the same set of conference proceed-

ings as Commoner, disagree that technology isthe dominant reason for environmental degrada-tion, emphasizing the importance of populationsize and growth, noting if there are too manypeople, even the most wisely managed technol-ogy will not keep the environment from beingoverstressed (Ehrlich and Holdren 1972a, 376).

Commoner, Ehrlich, and Holdren have beenextremely influential environmental thinkersfor a generation. Following their work came anunprecedented barrage of regulatory activity inthe United States, initiated to alter human deg-radation of the environment. First, the NationalEnvironmental Policy Act of 1970, followed bythe Clean Air Act, the Clean Water Act, theToxic Substances Control Act, the ResourceConservation and Recovery Act, and more thana dozen other less-well-known statutes, focusedAmericas attention on a range of threats to hu-man and ecosystem health. Interestingly, theregulation of the 1970s relied to a large extenton technology and engineered solutions to con-

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trol and manage end-of-pipe pollution. 1 The so-lution to dirty technology was, through the forceof law, to use more technology to clean it up.

In the pre Earth Day period, when Americanswere coming to grips with the unintended conse-quences of rapid technological development,blame tended to be placed on what Commonerreferred to as ecologically faulty technology. With twenty years more data to examine,Ausubel sees Earth Day 1970 to be a possible in-flection point in a number of trends, includingpopulation, and finds the message from history tobe that technology, wisely used, can spare theearth (Ausubel 1996a, 177).

This move toward technological optimism, asdiscussed later in this article, has gained groundin environmental circles. Although there arenotable extremes in any distribution, and seriouslimits to what scholars and practitioners oftenrefer to as technological fixes, a better under-standing exists of how technology, combinedwith improved design, can greatly aid the questfor sustainability. Indeed, the notion that tech-nological choice is crucial for environmental im-provement lies at the core of industrial ecology.Such thinking revises the informal mantra of U.S. technology policy from simply cheaper,

faster in the flow of innovations to the market-place to, at a minimum, cheaper, faster, cleaner and, to some visionaries, it offers the transforma-tive mechanism for achieving sustainability.

Origins of the IPAT Equation

The relationship between technological in-novation and environmental impact has beenconceptualized mathematically, as noted above,by the IPAT equation. IPAT is an identity simplystating that environmental impact (I) is theproduct of population (P), affluence (A), andtechnology (T).

I = PAT (1)

Generally credited to Ehrlich, it embodiessimplicity in the face of a multitude of morecomplex models, and has been chosen by manyscholars (Commoner et al. 1971a; Dietz andRosa 1994, 1997, 1998; Turner 1996; Wernick etal. 1997) as a starting point for investigating in-

teractions of population, economic growth, andtechnological development.

The IPAT identity has led, in turn, to themaster equation in industrial ecology (Heaton etal. 1991; Graedel and Allenby 1995). These havebeen followed by two concepts in sustainabilityresearch: the Factor 10 Club (1994) and FactorFour (von Weizs cker et al. 1997). The first tworeferences, IPAT and the master equation, staterelationships about technology and environmen-tal impact, whereas the use of Factor Four, Factor10, and even the Factor X debate described later,are attempts to quantify potential impacts.

In reviewing the literature, an interesting his-

tory emerges. The original formulation presentedby Ehrlich and Holdren (1971, 1972a,b) was in-tended to refute the notion that population wasa minor contributor to the environmental crisis. 2

Rather, it makes population which the authorscall the most unyielding of all environmentalpressurescentral to the equation by express-ing the impact of a society on the ecosystem as:

I = P F (2)

where I = total impact, P = population size, and Fis impact per capita. As the authors explain, im-pact increases as either P or F increases, or if one

increases faster than the other declines. Both vari-ables have been growing rapidly and are much in-tertwined. To show that the equation is nonlinearand the variables interdependent, Ehrlich andHoldren then expanded their equation as follows: 3

I = P (I, F ) F (3)

This variant shows that F is also dependenton P, and P depends on I and F as well. For ex-ample, rapid population growth can inhibit thegrowth of income and consumption, particularlyin developing countries. On the other hand,cornucopians such as Julian Simon maintainthat greater population is the key to prosperity(Simon 1980). Ehrlich and Holdren commentextensively on the tangled relationship of thesefactors and note that almost no factor has beenthoroughly studied (1972a).

Technology, at this stage, is not expressed as aseparate variable, but is discussed in relationshipto F, per capita impact. First, F is related to percapita consumption of, for example, food, en-

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ergy, fibers, and metals. Then, it is related to thetechnology used to make the consumption pos-sible and whether that technology creates moreor less impact. The authors note that improve-ments in technology can sometimes hold the percapita impact, F, constant or even decrease it,despite increases in per capita consumption (1972a, 372). Although this statement recognizesthe positive role technology can play, Ehrlich andHoldren generally conclude that technology candelay certain trends but cannot avert them.

Commoner also plays an important role inthe formulation of the IPAT equation.Commoner s work in his popular 1971 book The

Closing Circle, and much of his scientific analy-sis during the period of 1970 1972, were con-cerned with measuring the amount of pollutionresulting from economic growth in the UnitedStates during the postwar period. To do so, heand his colleagues became the first to apply theIPAT concept with mathematical rigor. In orderto operationalize the three factors that influenceI, environmental impact, Commoner furtherdefines I as the amount of a given pollutant in-troduced annually into the environment. Hisequation, published in a 1972 conference pro-ceedings (Commoner 1972a), is:

I PopulationEconomic good

PopulationPollutant

Economic good=

(4)

Population is used to express the size of theU.S. population in a given year or the change inpopulation over a defined period. Economic goodis used to express the amount of a particular goodproduced or consumed during a given year or thechange over a defined period and is referred to asaffluence. Pollutant refers to the amount of aspecific pollutant released and is thus a measureof the environmental impact (i.e., amount of

pollutant) generated per unit of production (orconsumption), which reflects the nature of theproductive technology (Commoner 1972a,346). Used in this way, the equation takes on thecharacteristics of a mathematical identity. Onthe right-hand side of the equation, the twoPopulations cancel out, the two Economic goodscancel out, and what remains is: I = Pollutant.

I PopulationEconomic good

PopulationPollutant

Economic good=

Thus, for Commoner, environmental impactis simply the amount of pollutant released ratherthan broader measures of impact; for example,the amount of damage such pollution created orthe amount of resource depletion the pollutioncaused.4 His task, then, is to estimate the contri-bution of each of the three terms to total envi-ronmental impact.

Much to the consternation of Ehrlich andHoldren, Commoner s effort to measure impactas amount of pollution released leads to the con-clusion that technology is the culprit in almostevery specific case he examines. Commoner goeson to compare the relative contributions of the

three IPAT variables arithmetically: Population,affluence (Economic good/Population),and tech-nology (Pollutant/Economic good), in examplessuch as detergent phosphate, fertilizer nitrogen,synthetic pesticides, tetraethyl lead, nitrogenoxides, and beer bottles. He concludes that thecontribution of population and affluence topresent-day pollution levels is much smallerthan that of the technology of production. Hecalls for a new period of technology transforma-tion to undo the trends since 1946 in order tobring the nation s productive technology muchmore closely into harmony with the inescapable

demands of the ecosystem (1972a, 363).Following the publication of The Closing Circle

(Commoner et al. 1971a), full-scale academic warerupted between Ehrlich and Holdren on the onehand and Commoner on the other. In a fierce Cri-tique and Response published in the Bulletin of the

Atomic Scient ists in March 1972, Ehrlich andHoldren reject the mathematical basis throughwhich Commoner finds population a modest con-tributor to environmental impact. In their piece,One-Dimensional Ecology, Ehrlich and Holdrencharge that Commoner, in his zeal to blame faultytechnology, overemphasizes pollution, miscon-ceives certain aspects of demography, understatesthe growth of affluence, and resorts to biased se-lection of data . . . and bad ecology. Their evidentfear comes from the possibility that uncritical ac-ceptance of Commoner s assertions will lead topublic complacency concerning both populationand affluence in the United States (1972b, 16).

Commoner (1972b), in his Response pub-lished in the same issue of the Bulletin, offers aspirited defense of his mathematical and eco-

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logical competence and evokes supporting re-views by Sir Eric Ashby and Rene Dubos to theintemperate onslaught by Ehrlich andHoldren. Commoner reminds the reader that itwas Ehrlich who first wrote: Pollution can besaid to be the result of multiplying three factors;population size, per capita consumption, and anenvironmental impact index that measures, inpart, how wisely we apply the technology thatgoes with consumption (Commoner 1972b,42). Commoner originally quoted this in anApril 1971 article in Environment written withcolleagues Michael Corr and Paul Stamler.Commoner s interest in the Environment piece

and in a follow-up piece for a symposium held bythe U.S. think tank Resources for the Future wasto try to operationalize the relationship firstproposed by Ehrlich and Holdren, that is , to finda way of entering the actual values for the sev-eral factors and thus computing, numerically,their relative importance (Commoner 1972b,42). Commoner s team paraphrased this rela-tionship, introducing the terms consumption and production into the variant as follows as:

Population size per capita consumption environmental impact per

unit of production = level of pollution (5)

At this stage Commoner brought to light aletter Ehrlich and Holdren sent to colleagues inwhich they reveal that they had urged Com-moner not to engage in debate about which of the factors was most important because it wouldbe counterproductive to achieving environmen-tal goals. Commoner takes great umbrage at theidea of avoiding public discussion of scientificfindings in favor of private agreements that, inturn, erode democracy and the survival of acivilized society (1972b, 56). Commoner iden-tifies what he believes to be behind the debate:that Ehrlich is so intent upon population con-trol as to be unwilling to tolerate open discus-sion of data that might weaken the argument forit (1972b, 55).

Some of the issues raised between the twosides of this debate reflect the formative natureof the ideas. Note that across the several differ-ent articles and books mentioned, there is notone single way of stating the variables or evenconsistency as to whether we are attempting to

measure I, environmental impact or P, Pollu-tion. The very first time the reference I = P A T appears in writing is as part of the Critiqueand Response in 1972, in which Ehrlich andHoldren take Commoner s equation from a foot-note from The Closing Circle:

pollution = ( population) ( production/capita) ( pollution emission/production) (6)

and, say, for compactness, let us rewrite thisequation :

I = P A T (7)

From this basis Ehrlich and Holdren dissect

Commoner s mathematics. They point out thatCommoner uses his definitions of P, A , and T asindependent variables such that their effects on Iare independent of each other. Ehrlich andHoldren are careful to describe them as interde-pendent as in formula (3) above. Ehrlich andHoldren also emphasize the multiplicative natureof population. In a 1974 piece, they identify howpopulation acts as a multiplier of consumptionand environmental damages associated with hu-man activity such that even if no one of the IPATterms goes up very much, it is the simultaneousincreases in all the factors that cause extensive

environmental impact. They make the case thatusing them as independent variables tends to un-derestimate the impact of population. 5

In another article, Holdren and Ehrlich(1974) offer yet another formulation of what theyterm the population/environment equation :

environmental disruption = population consumption/person

damage/unit of production (8)

First, environmental disruption substitutes for I,impact, and damage, in the third term, is a pre-sumed outcome of each unit of consumption.

Note, also, the cross- substi tut ion among themany formulations of consumption and produc-tion. Sometimes production and consumptioncancel each other out, and sometimes they donot. Sometimes the affluence term is used forone or the other or for both as in the form pro-duction/consumption or production (con-sumption). In Commoner s original paraphraseof Ehrlich (equation (5)), in which he makesconsumption part of affluence and production

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part of technology and the terms do not cancelout, he goes on to make the now outdated state-ment that since imports, exports, and storageare relatively slight effects, total consumptioncan be taken to be approximately equal to totalproduction (Commoner et al. 1971b, 4). Today,imports and exports are not slight effects, so wewould not even try to equate U.S. productionwith U.S. consumption. Even so, the relation-ship of production to consumption is not a focusof these early articles. In fact, only in the late1990s did an analytic discussion of consumptionbegin to take shape in the scientific community(Stern et al. 1997; Berkhout 1998).

Apples and Oranges

In comparing Commoner with Ehrlich andHoldren, there are often differences in time andspatial scale. Commoner tends to write aboutthe present deteriorating environmental condi-tions in the United States, and sometimes fo-cuses more locally on a given pollutant. He giveslight attention to resource use with his heavyfocus on pollution. Ehrlich and Holdren have abroader sweep and are less specific in space andtime. They write in several of their articles about

the underestimated role of diminishing returns,threshold effects, and synergisms, as well as therelation between ecosystem complexity and sta-bility. They suggest that direct effects of envi-ronmental damage such as lead poisoning andair pollution are likely to be less threatening, ul-timately, than the indirect effects on humanwelfare from interference with ecosystem struc-ture and function. They note numerous ex-amples of the public services of nature(Holdren and Ehrlich 1974), today betterknown as ecosystem services (Daily 1997).

Commoner and Ehrlich and Holdren evendiffer on a common meaning of affluence.Ehrlich and Commoner generally consider a percapita output measure. Commoner does not seetrue affluence as the culturally prescribed ac-cumulation of television sets and fancy cars,more akin to consumption. Rather, he attemptsto differentiate the technology used to delivergoods from the actual contribution of thosegoods to human welfare as a means of separatingconsumption from true affluence. For ex-

ample, although the consumption of non-returnable beer bottles went up almost 600 per-cent in the period 1950 1967, actual consump-tion of beer per capita increased a mere fivepercent. Thus, the affluence gain to the beerdrinker has been slight, whereas the technologychosen to package and deliver the beer, which isof no use to the consumer, has changed dramati-cally at the expense of the environment.

Despite some differences in orientation be-tween Commoner and Ehrlich and Holdren, thechicken-and-egg nature of this debate whetherpopulation or technology is a bigger contributorto environmental damage is revealing. Does

an increased population call for improved tech-nology, or does improved technology increasecarrying capacity? 6 (Boserup 1981; Kates 1997).Even our latter-day technology optimist, JesseAusubel, is stymied by the technology/popula-tion link (1996a, 1996b). Just as he demon-strates a revolution in factor productivity inenergy, land, materials, and water, especiallysince the time of the Commoner/Ehrlich debate,he goes on to describe how the new technologiesserve to make the human niche elastic. If wesolve problems, our population grows and cre-ates further, eventually insurmountable prob-

lems (1996a, 167). Would technology that isnot, in Commoner s phrase, ecologicallyfaulty, (1972a, 362), but rather ecologicallywise, merely delay the inevitability of environ-mental destruction, or is better technology ourbest horse in the race toward sustainability?

In a review of several models of anthropo-genic driving forces of environmental impact,Deitz and Rosa single out the IPAT equation be-cause it is easily understood, frequently used forillustrative purposes and can discipline ourthinking (Deitz and Rosa 1997). They drawthis conclusion despite their finding that the ef-fects of population and economic growth on en-vironmental degradation have not beenextensively researched and are thus uncertain.

B. L. Turner (1996) finds the IPAT equationuseful as a macro-scale assessment, noting that re-gional and local scale assessments generally high-light other drivers of environmental changes suchas policy, institutions, and complexity of socialfactors. Meyer and Turner point out that the IPATequation is largely the product of biologists and

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ecologists and uses terms undefined in social sci-ence. They comment that neither A (affluence)nor T (technology) is associated with a substan-tial body of social science theory (Meyer andTurner 1992).

Conceptually as well as numerically, P, popu-lation, and A, defined as a per capita measure of wealth, consumption, or production, have gen-erally been more accessible to researchers thanthe T term. The product ( P A) represents anaggregate measure of total economic activity,such as total GDP. In this case, T = I/P A or T = unit of environmental impact per unit of eco-nomic activity. Here, T, technology, becomes

the residual of an accounting identity; it repre-sents everything that affects the environmentthat is not population or affluence. As Deitz andRosa observe, most social scientists are frus-trated by the truncated visions of the rest of theworld offered by the T in the IPAT model (1994, 287). In this sense, whether technology,through the T term, is truly endogenous to themaster equation could be questioned (Grubler2001). Thus, Deitz and Rosa recommend that anindependent measure of T be used and that re-searchers be required to specify T rather thansolve for it.

The notion of T as residual is a reminder of an important antecedent to the IPAT quest todisaggregate the elements of environmental im-pact. Macroeconomists have been involvedsince the 1930s with efforts to disaggregate fac-tors of economic growth and productivity in theeconomy (Griliches 1996). Robert Solow s

Nobel Prize in economics, for example, was asso-ciated with his statistical explanation of thecauses of U.S. manufacturing growth from19091949 (Clark 1985). He found that laborand capital, the traditional factor inputs of neo-classical economics, explained only about 10percent of this growth. The rest, some 90 per-cent, was residuala factor representing allother contributions to growth such as education,management, and technological innovation.Later research identified about 30 40 percent of the explanation for income growth to be attrib-utable to technological change, with the poorlyunderstood interdependence of the variables be-ing the most difficult challenge (Stoneman1987; Abramovitz 1993). Although there is no

clear evidence that the IPAT progenitors wereexposed to growth accounting in economics, wesee that poor definition of a residual term is notunique to the environmental field.

Another critique leveled by Deitz and Rosa isthat although the IPAT equation does allow forsome disaggregation of the forces of environ-mental change, including human impacts, thedisaggregation is too simple and does not allowfor interactions among population, affluence,and technology (Deitz and Rosa 1998). As itstands, a direct relationship is formed such thata 10 percent increase in P, A, or T creates a 10percent increase in environmental impact. Deitz

and Rosa cite several studies that build upon theIPAT model to enable it to capture more com-plexity and interaction among the variables.They actually reformulate the IPAT equation asSTIRPAT meaning Stochastic Impacts byRegression on Population, Affluence and Tech-nologyto be able to disaggregate P, A, and T and to be able to use regression methods to esti-mate and test hypotheses. Their reformulation isI = aPb A cT de, where the variables ad can be ei-ther parameters or more complex functions esti-mated using standard statistical procedures and eis the error term (Deitz and Rosa 1994, 1997,

1998). They have used the STIRPAT model tobridge the social and biological sciences in, forexample, studies of global climate change.

The IPAT equation has also been a source forthe development of the literature on energy de-composition analysis, which disaggregated en-ergy intensity and extended and refined themathematics of IPAT (Greening et al. 1998,1999; Gurer and Ban 1997). The use of the IPATequation in research related to climate change,specifically energy-related carbon emission stud-ies, may be the most enduring legacy of IPAT.Such formulations are typically stated as(Holdren 2000): Energy use = Population GDP/person energy/GDP; and Carbon emis-sions = Population GDP/person carbon en-ergy. In this way IPAT has played a prominentrole, particularly in the Intergovernmental Panelon Climate Change assessments (IPCC 1996).

Ultimately, the evidence presented suggeststhat the IPAT equation can be used to supportmany different points of view. Ehrlich andHoldren show how it supports the population

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view. Commoner demonstrates how it supportsthe harmful technology or Faustian view. Econo-mist Julian Simon, representative of thecornucopian view, believes that increasing popula-tion and wealth is the driving force for new tech-nological development (Simon 1981). That theIPAT formulation can be interpreted in so manyways represents a weakness and a strength: on theone hand, it may simply be too broad and generalto account for the interrelationships among thevariables. On the other hand, it has not revealeda bias and need not be definitive to be extremelyuseful as a thought model. There really has beenno underlying disagreement that each of the terms

belongs to the equation in some way and so, as aconceptual analytic approach, IPAT providesreadily identifiable common ground.

The technology factor is also subject to mul-tiple interpretations. Ehrlich and Holdren cite afundamental problem associated with reliance ontechnology by recognizing that no technology cancompletely eliminate the environmental impactof consumption. They choose the example of re-cycling, which always results in some loss of ma-terials, if for no other reason than the sad butunavoidable consequences of the second law of thermodynamics (1972a, 370). Commoner is the

harshest on ecologically faulty technology andits singular environmental impact, but, on theother hand, is quite receptive to developing newtechnologies which incorporate not only theknowledge of the physical sciences (as most domoderately well), but ecological wisdom as well (1972a). Because IPAT factors take us well be-yond technological choice, we quickly cross fromthe realm of technologists, especially scientistsand engineers, into the realm of social scientists,politicians, and the needs, wants, and desires of people. The ubiquity of C. P. Snow s two cul-tures problem is especially evident in the IPATrealm because organizing the relationships of population, environmental impact, and socialwelfare puts analysts at the juncture of the scien-tific and humanistic realms. As cultural historianLeo Marx points out, we often name environmen-tal problems after their biophysical symptoms,such as soil erosion or acid rain, and thus addressthem to scientists. Naming practices reflect thedominant outlooks of the culture. For example,Marx points out that if we, as a society, were less

technology-friendly, we might have avoided theflowery greenhouse effect in favor of the prob-lem of global dumpsites or the celestial emphy-sema syndrome (Marx 1994, note 3). The rootcause of each of these problems, however, doesnot come from nature, but rather the human be-havior and the complex practices that go alongwith it (Marx 1994). We lean to technologists inpart because of an inadequate understanding of the part played by ideological, moral, religious,and aesthetic factors in shaping response to envi-ronmental degradation (1994, 18).

The Transit ion to TechnologicalOptimismIf the approach of the environmental move-

ment of the 1970s was to juxtapose the gains of economic growth with the devastating reality of pollution, this approach changed in the 1980s.The Brundtland Commission report in 1987concluded that if humanity were to have a posi-tive future, then economy and environment hadto be made more compatible. Sustainable waspaired with development to describe this state,and since that time there has been increasingacceptance that economy and environment can

be mutually compatible (World Commission onEnvironment and Development 1987).

At the same time, the IPAT equation makes uskeenly aware of our limited choices. The year fol-lowing the Brundtland report, one environmentalchieftain, under the heading A Luddite Re-cants, conceded that economic growth has itsimperatives; it will occur . . . seen this way, recon-ciling the economic and environmental goals so-cieties have set for themselves will occur only if there is a transformation in technology a shift,unprecedented in scope and pace, to technolo-gies, high and low, soft and hard, that facilitateeconomic growth while sharply reducing the pres-sures on the natural environment (Speth 1988).Here, James Gustave Speth, then president of theWorld Resources Institute, converts the 1970ssuspicion, as expressed by Commoner s condem-nation of ecologically faulty technology, into anexpression of hope for transformed technology(see also Speth 1990, 1991).

This line of argument is presented in a publi-cation of the World Resources Institute called

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Transforming Technology: An Agenda for En-vironmentally Sustainable Growth in the 21stCentury (Heaton, Repetto, and Sobin 1991).Heaton and colleagues recite a variant of theIPAT equation resurrected by Speth in a back-ground paper a year earlier (Speth 1990) andexplain its critical importance to the future of the environment in a section of their articletitled Why Technological Change Is Key. They write:

Human impact on the natural environ-ment depends fundamentally on an inter-action among population, economicgrowth, and technology. A simple iden-tity encapsulates the relationship:

Pollution Pollution

GNPGNP

PopulationPopulation= (9)

Here, pollution (environmental degrada-tion generally) emerges as the product of population, income levels (the GNP percapita term) and the pollution intensityof production (the pollution/GNP term).

In principle, pollution can be con-trolled by lowering any (or all) of thesethree factors. In fact, however, heroic ef-forts will be required to stabilize globalpopulation at double today s level, andraising income and living standards is anear-universal quest. Indeed, economicgrowth is a basic goal for at least 80 per-cent of the world s population. Thesepowerful forces give economic expansionforward momentum. In this field of forces,the pollution intensity of productionlooks to be the variable easiest to manipu-late, which puts the burden of changelargely on technology. In fact, broadly de-fined to include both changes within eco-

nomic sectors and shifts among them,technological change is essential just tohalt backsliding: Even today s unaccept-able levels of pollution will rise unless thepercentage of annual growth in global andeconomic output is matched by an annualdecline in pollution intensity (Heaton,Repetto, and Sobin 1991, 1).

Thus, whereas the IPAT equation can sendus in several directions, recent interpretations

cast the T term in a very positive light. In essence,a new generation of technological optimists findsthat experiments in changing human behavior tovary the course of P and A are highly uncertain.Stated another way, Walter Lynn, while Dean of the Cornell University faculty, cited the lack of progress in social engineering, and the success,even if temporary, of technological fixes. He ob-served: Currently, technology provides the onlyviable means by which our complex interdepen-dent society is able to address these environmen-tal problems (Lynn 1989, 186).

Enter Industrial Ecology

The concepts of the IPAT equation are at thecore of the emerging field of industrial ecology.Industrial ecology has been described as themarriage of technology and ecology and exam-ines, on the one hand, the environmental im-pacts of the technological society, and, on theother hand, the means by which technology canbe effectively channeled toward environmentalbenefit. According to the first textbook in thisnew field (Graedel and Allenby 1995), indus-trial ecology has adopted the following IPATvariant as its master equation :

Environmental impact PopulationGDP

personEnvironmental impactunit of per capita GDP

=

(10)

This master equation incorporates the samerelationships as the WRI equation, with somechanges in terminology. Once again we see thevariation between defining pollution, P, as WRIhas done, in contrast to defining environmentalimpact, as in the master equation. WRI statesthe equation as an identity the populationscancel and the GNPs cancel so that Pollution=Pollution. The master equation is not strictlystated as an identity. Also, Graedel and Allenbyuse gross domestic product (GDP) for the afflu-ence term rather than WRI s gross national prod-uct (GNP), which reflects a shift by the UnitedStates in 1991 to the use of GDP in order to con-form to the practices of most other countries.Although GNP is defined as the total final out-put produced by a country using inputs owned bythe residents of that country, GDP counts theoutput produced with labor and capital located

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inside the given country, whoever owns the capi-tal (Samuelson and Nordhaus 1998).

WRI s technology term is a measure of thepollution intensity of production (the pollution/GNP term). Graedel and Allenby define theirthird term, qualitatively, as the degree of envi-ronmental impact per unit of per capita gross do-mestic product, which they call an expression of the degree to which technology is available topermit development without serious environ-mental consequences and the degree to whichthat available technology is deployed (Graedeland Allenby 1995, 7). Although it is interestingto observe the back and forth of the use of I, im-

pact versus P, pollution in the history of the IPATequation, it is not surprising that such a macroview makes it difficult to capture true differencesin types and dynamics of specific impacts that aredifficult, if not impossible, to aggregate.

Characteristic of each T term is the assump-tion that the pollution it defines can be reduced.Curiously, this usage leaves room for being lessbad, for example, through pollution reduction oreco-efficiency, but does not really express thepotential human and environmental benefit thatcan come from technology (McDonough andBraungart 1998). All in all, WRI s formulation

and that of the master equation are similar alongthe lines we have seen since the Commoner/Ehrlich and Holdren debate, but give furtherdefinition to A and T. A sense of progress existsin that Ehrlich and Holdren as well as Com-moner, although using a multiterm equation,were really most interested in pursuing a singlecause. Still, the more recent emphasis on pollu-tion per unit GNP or GDP is not a satisfactoryuniversal definition of technology, leaving roomfor continual reconsideration.

Let us examine the three terms of the masterequation and IPAT more broadly. In practice, atthe global level, there is strong upward pressureon the first term, population, even as we debatethe range of those increases (Marchetti et al.1996). Similarly, the common desire to improvequality of life translates into an increasing secondterm, affluence, as well. Affluence, as measured bygross domestic product (GDP) per person, spreadsthe worth of a country s economy over the popu-lation. Clearly, this, too, is a generalization. Percapita figures miss growing disparities between

rich and poor in many countries. GDP has beencriticized as distortionary for measuring onlyquantifiable transactions, leaving out harder-to-measure, but critical, assets such as an educatedpopulace, healthy citizens, and a clean environ-ment (Cobb, Halstead, and Rowe 1995). 7 None-theless, to the extent that, as a blunt measure, realGDP per person rises, it implies that wealth and,subsequently, quality of life are more likely to beimproving. Therefore, as in the I = PAT equation,both of the first terms presented here are headedupward, although estimates of how much varywidely.8 In the emerging industrial ecology view,using technology to reduce environmental impact

can, theoretically, not only compensate for theimpact of more people, but also the impact of moreaffluent people. Increasing wealth without back-sliding as described by WRI, or even while de-creasing overall impact, is a worthy, if challenginggoal. According to Graedel and Allenby:

The third term, the amount of environ-mental impact per unit of output, is pri-marily a technological term, thoughsocietal and economic issues providestrong constraints to changing it rapidlyand dramatically. It is this third term in

the equation that offers the greatest hopefor a transition to sustainable develop-ment, and it is modifying this term thatis the central tenet of industrial ecology(Graedel and Allenby 1995, 8).

Until recently, the third term, technology, hasbeen seen as a continuous source of pollution:technology, for example, to mine, manufacture,and drive with all the environmental harms suchactivities create. Other differences are concealedby the macro nature of the IPAT equation and itsvariants. In the master equation, the T term is de-fined as the amount of environmental impact eachunit of a country s wealth creates averaged overthe population as a whole. In reality, this is anoversimplification. Countries with clean, energy-efficient production have been able to producegreater wealth with less per-unit environmentalimpact. The poorest countries are least likely tohave clean air, water, and sanitary systems. Buteven here anomalies exist, summarized in discus-sions of the environmental Kuznets curve, which

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considers a nuanced relationship between A, af-fluence, and I, impact, such that an environmen-tal emission might rise as income increases until aparticular level is reached, at which point emis-sion levels begin to fall (Arrow et al. 1995).

As indicated below, no universal rule exists:Impacts such as waste and carbon dioxide emis-sions increase with wealth, whereas other indica-tors, such as urban concentrations of particulatematter and sulfur dioxide, decline over specifiedincome levels (see figure 1). Some indicators,such as urban concentrations of particulate mat-

ter or sulfur dioxide, as shown in figure 1, followthe environmental Kuznets curve hypothesis,worsening at first and then improving as incomeincreases (Hosier 1996). Many researchers havebeen interested in the relationship of affluenceand environmental impact and have determinedthat the condition of impact worsening and thenimproving with income is most typical of short-term, local indicators such as sulfur, particulates,and fecal coliforms, but not to accumulatedstocks of waste or long-term dispersed indicatorssuch as CO 2 (Rothman and de Bruyn 1998).

Figure 1 Relationship of affluence (per capita income) to various environmental impacts.Sources: Hosier (1996) from Shafik and Bandyopadhyay, background paper; World Bank data.

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Earlier discussions of T, and IPAT in generalfrom Ehrlich onward portray a curiously passiverole for the technology producer. Either technol-ogy is used abstractly, as in Ehrlich and Holdren swriting, or it is assumed to be static in that theproducers just keep on doing what they havedone before. Interventions, then, are policiesfrom above rather than revisions of the mind-sets of the technologists. In contrast, industrialecology has deep roots in engineering and thephysical sciences, so it is not surprising that itspractitioners would put stock in the T term, withwhich they are most familiar professionally. Butneither is it easy to assure that any given tech-

nology, let alone T, technology collectively, willbe beneficial rather than harmful. By offering asystems approach to environmental/technicalinteractions, industrial ecology research can pro-vide an essential link between the episodic use of promising technology and the long-term, lessdefined goal of sustainable development.

Another critical component industrial ecolo-gists have brought into the discussion of anthropo-genic environmental impacts is the participationof private industry. In describing the industrial character of industrial ecology, the first issue of the

Journal of Indust rial Ecology notes that it views

corporate entities as key players in the protectionof the environment, particularly where techno-logical innovation is an avenue for environmentalimprovement. As an important repository of tech-nological expertise in our society, industrial orga-nizations can provide crucial leverage in attackingenvironmental problems by incorporating envi-ronmental considerations into product and pro-cess design (Lifset 1997, 1).

The Factor X

Neither in the IPAT equation, nor inCommoner s quantitative work, nor in the masterequation in industrial ecology is there an attemptto quantify the relationship of technology andenvironmental impact in a prospective way, al-though this has entered some of the global cli-mate change work cited earlier. Still, a thresholdfor sustainability is that it meets the needs of thepresent without compromising the ability of fu-ture generations to meet their own needs (WorldCommission on Environment and Development

1987). Therefore, using these equations predic-tively would enhance the theoretical basis of IPAT ideas, for example, determining how muchtechnology versus how much increase in popula-tion and affluence would be reasonable goals forcountries and for the global commons. Recently,two agendas have been established that set targetsfor technology and environmental impact.

F. Schmidt-Bleek, while with the WuppertalInstitute, presented the Carnoules Declarationof the Factor 10 Club in 1994. The Factor 10Club has focused on the need to substantiallyreduce global material flows. Its advocates be-lieve that the current productivity of resources

used must be increased by an average of a factorof ten during the next 30 to 50 years. This isfeasible if we mobilize know-how to generatenew products, services, as well as new methodsof manufacturing (Factor 10 Club 1994, 8). Wesee here reliance on know-how and methodsof manufacturing that again emphasizes the T term of the IPAT equation, in this case to createa specific sustainability target.

Weizscker, Lovins, and Lovins (1997) statein their book, Factor Four: Doubling Wealth,Halving Resource Use, that the amount of wealthextracted from one unit of natural resources can

quadruple. Their goal that we can live twice aswellyet use half as much might be expressedin IPAT terms as achieving 2( A ) with only.5( T ). They define technological progress nei-ther as a reduction in pollution nor as a gain inlabor productivity, but, overall, as a gain in pro-ductivity of resources. Up until now, tremendousgains in productivity have come from substitut-ing resources for human labor. They are con-cerned that such substitution has gone too farand been inconsiderate of overusing resourcessuch as energy, materials, water, soil, and air.Their research is devoted to an efficiency revo-lution that shows the potential for fourfoldgains in resource use.

Factor Four and the Factor 10 are specific, if ambitious, expressions of the potential impact of T, the technology term. They are also future-oriented, setting a goal for corporate and policydirection. The four- to tenfold increase in aggre-gate economic impact, PA, can also be thought of as a twofold increase in P, population, over thenext 50 years, and a two- to fivefold increase in A,

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affluence. Picking up on Factor Four and the Fac-tor 10, Lucas Reijnders of the University of Amsterdam writes of The Factor X Debate (Reijnders 1998), in which researchers have goneeven further than a factor of four or ten to proposelong-term reductions in resource use as high as 50times. This would occur through dematerializa-tion, eco-efficiency, or increased natural resourceproductivity relying mainly on the T of the IPATequation. Of course, until environmental impactis defined with great specificity, the choice of dif-ferent X factors, including the baseline of FactorFour and the Factor 10, is arbitrary. Reijndersnotes that whereas the debate in the United

States is still largely within the NGO community,the concept of Factor X and the importance of quantifying objectives has influenced policy inseveral European nations, including Austria, Ger-many, and the Netherlands.

Do Factor X policies put the entire onus forenvironmental improvement on the technologyvariable? Some would tag WRI and the indus-trial ecologists as implying that nothing can bedone about population and increasing wealth.This is too pessimistic a reading. The effective-ness of population programs has been demon-strated in many parts of the world, for example,

in China, Japan, and Thailand (Miller 1994). Asa matter of basic fairness, few would want todeny the improvement in the standard of livingfor the world s peoples implied in the affluenceterm. Neither can the three terms be consideredin isolation. Rather, interactive effects exist, asdemonstrated by Ehrlich and Holdren. Still, asReijnders concludes, although there is no agree-ment on the relative importance of technologyin achieving a Factor X for economies as awhole, one still may note that the Factor X de-bate is characterized by a remarkable technologi-cal optimism. This is especially so if one viewsthis debate against the background of a widelyheld supposition that environmentalism has anantitechnological bias (Reijnders 1998, 18).

The Call of the Optimist

Just as all ecological problems are contextual,so too are the issues confronted by IPAT, whichmay shed light on why it has multiple interpre-tations. Since it was introduced in the early days

of the environmental movement, much haschanged, in large part because of the alarmsounded in the post Silent Spring era by Ehrlichand Holdren, Commoner, and many otherthoughtful researchers and policy makers. Still,much of the change was motivated by pessi-mism, captured in this statement of Holdren andEhrlich at the end of their 1974 article:

Ecological disaster will be difficultenough to avoid even if population limi-tation succeeds: if population growthproceeds unabated, the gains of improvedtechnology and stabilized per capita con-sumption will be erased, and averting di-saster will be impossible (Holdren andEhrlich 1974, 291).

Indeed, these are still controversial issues. En-vironmentalists of the 1970s who were pessimis-tic continued to sound alarms in the 1990s(Ehrlich and Ehrlich 1990; Commoner 1992;Meadows et al. 1992). Deep ecologists will notwake to find themselves warm to technologicaloptimism. But a great deal more consciousnessabout environmental issues exists internationally,especially among global institutions such as theUnited Nations, the World Bank, and other fi-

nancial players (Schmidheiny and Zorraguin1996). Indeed, the notion that environmentalproblems can be addressed and even advancedthrough technical and procedural innovation hasachieved its own name in the European environ-mental sociology literature ecological modern-ization (Hajer 1996; Mol and Sonnenfeld 2000).In the United States, environmental policy, forall its warts, has made an enormous contributionat the end of the pipe, and is slowly migrating to-ward more integrative policy. Similarly, in corpo-rate environmental policy, researchers can nowmeasure the early stages of a change in emphasisfrom regulatory compliance toward overall pro-cess efficiency (Florida 1996), even at the ex-pense of sales in the traditional end-of-pipeenvironmental industry (U.S. Department of Commerce 1998).

Upon reflection, I believe that Commoner(1972a) anticipates the work defined by Ausubel,WRI, and industrial ecologists. He calls for anew period of technological transformation of the [U.S.] economy, which reverses the counter-

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ecological trends developed since 1946 atransformation that reconnects people and theirecosystems:

Consider the following simple transforma-tion of the present, ecologically faulty, re-lationship among soil, agricultural crops,the human population and sewage. Sup-pose that the sewage, instead of being in-troduced into surface water as it is now,whether directly or following treatment, isinstead transported from urban collectionsystems by pipeline to agricultural areas,whereafter appropriate sterilization pro-ceduresit is incorporated into the soil.Such a pipeline would literally reincorpo-rate the urban population into the soil secological cycle, restoring the integrity of that cycle . . . Hence the urban populationis then no longer external to the soil cycle. . . But note that this rate of zero environ-mental impact is not achieved by a returnto primitive conditions, but by an actualtechnological advance.

Conclusions

This article underscores that technology, al-

though associated with both disease and cure forenvironmental harms, is a critical factor in envi-ronmental improvement. Thus, important rea-sons can be found to continue to developframeworks such as industrial ecology, that focuson cures. The overall shift from pessimism to op-timism, captured here through changing inter-pretations of the IPAT equation and its variants,is shown to be partly fatalistic, in that few alter-natives exist to the imperative established by theBrundtland Commission; partly pragmatic, inthat technological variables often seem easier tomanage than human behavior; and partly a con-tinued act of faith, at least in the United States,in the power of scientific advance.

Notes

1. Indeed, the very prescriptive laws of this periodhave been criticized by researchers for becomingso specific in their standards as to preclude tech-nological innovation (NACEPT 1991; Heaton etal. 1991; U.S. Department of Commerce 1998).

2. A precursor to the IPAT formulation by sociolo-gist Dudley Duncan in 1964 was the POETmodel (population, organization, environment,technology). According to Deitz and Rosa(1994), the model showed that each of thesecomponents are interconnected but did notspecify quantifiable relationships.

3. To trace the origins of these equations accuratelyis challenging. The IPAT ideas emerged in 1970and 1971. Particularly relevant was an exchangeby Commoner and Ehrlich and Holdren in theSaturday Review during 1970 followed by a meet-ing at the President s Commission on PopulationGrowth and the American Future held on No-vember 17, 1970, the findings of which were notpublished until 1972. However, Ehrlich andHoldren and Commoner produced numerouspublications in the meantime, which helpedsteer the IPAT debate in new directions. Ehrlichand Holdren used I = P(I,F) F(P) in the 1972findings, but a slightly different version, I = P F(P) in their earlier article from Science in Marchof 1971, which is otherwise almost identical tothe 1972 conference report. Both equations tryto express a similar point, that P and F are inter-active and can increase faster than linearly.

4. In fact, one of the reviewers of this article sug-gested that this use of the IPAT equation mightbetter be called EPAT, showing the emphasison E for Emissions rather than the totality of I for all impacts.

5. The authors use the example of the impact of leademissions from automobiles from 1946 to 1967 andfind that population has increased 41 percent; con-sumption, measured as vehicle-miles per person,has doubled; and lead emissions per vehicle-mileincreased 83 percent. Hence, 1.41 2.0 1.83 =5.16, or, subtracting 1.0, a 416 percent increase intotal impact. This illustrates that although no vari-able more than doubled, the cumulative impact ismultiplicative. Had population not grown but beenheld constant, then total impact would only havebeen 1.0 2.0 1.83, or 3.66, reflecting a 266 per-

cent increase, illustrating the multiplier effect (seeHoldren and Ehrlich 1974, using corrections to thevariables suggested by Commoner 1972b).

6. Editors note: For an application of decomposi-tion analysis to materials flows, see Hoffr n,Luukkanen, and Kaivo-oja, DecompositionAnalysis of Finnish Material Flows: 1960 1996,

Journal of Industrial Ecology, this issue.7. Further, these authors point out that the GDP

measures socially and environmentally destruc-tive behavior as an economic gain. Pollution, for

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example, shows up as a double boost to theeconomy. The first boost comes when a pollut-ing company makes a profit on the product theyare selling and the second boost comes when thecompany spends large amounts of money on en-vironmental cleanup.

8. Graedel, however, has some revisionist thinkingabout A, the affluence term (Graedel, 2000).Simply assigning it a financial measure such asGNP or GDP per capita may overemphasize thecontribution of the market, and, as a result, de-emphasize the opportunity for changing atti-tudes even as income rises. Graedel hassuggested that the essence of the A term residesin its cultural and behavioral attributes, whichhe has called the Madonna factor after thepop singer s well-known phrase a material girlin a material world.

References

Abramowitz, M. 1993. The search for the sources of growth: areas of ignorance, old and new. Journalof Economic History53(2): 217 243.

Arrow, K. et. al. 1995. Economic growth, carrying capac-ity and the environment. Science 268: 520521.

Ausubel, J. H. 1996a. Can technology spare theearth? American Scientist 84: 166 178.

Ausubel, J. H. 1996b. The liberation of the environ-ment. Daedalus 125: 117.

Berkhout, F. 1998. Book review of EnvironmentallySignificant Consumption: Research Directions;Resource Flows: The Material Basis of IndustrialEconomies; Towards Sustainable Consumption;Sustainable Consumption and Production. Jour-nal of Industrial Ecology2(2): 119 125.

Boserup, E. 1981. Population and technological change.Chicago: The University of Chicago Press.

Brooks, H. 1987. What is the national agenda for sci-ence, and how did it come about? American Sci-entist 75: 511 517.

Clark, N. 1985. The political economy of science andtechnology. Oxford, Great Britain: Basil

Blackwell.Cobb, C. W., T. Halstead, and J. Rowe. 1995. If theGDP is up, why is America down? Atlant icMonthly 276: 5960.

Commoner, B., M. Corr, and P. J. Stamler. 1971a. Theclosing circle: nature, man, and technology. NewYork: Knopf.

Commoner, B., M. Corr, and P. J. Stamler. 1971b. Thecauses of pollution. Environment13(3): 2 19.

Commoner, B. 1972a. The environmental cost of eco-nomic growth. In Population, Resources and the En-

vironment, edited by R. G. Ridker. Washington DC:U.S. Government Printing Office, pp. 339 363.

Commoner, B. 1972b. A bulletin dialogue on TheClosing Circle : Response. Bulletin of the AtomicScientists 28(5): 17, 42 56.

Commoner, B. 1992. Making peace with the planet. New York: New Press.

Daily, G., ed. 1997. Nature s services: Societal depen-dence on natural ecosystems. Washington, DC: Is-land Press.

Dietz, T. and E. Rosa. 1994. Rethinking the environ-mental impacts of population, affluence andtechnology. Human Ecology Review 1: 277300.

Dietz, T. and E. Rosa. 1997. Environmental impacts of population and consumption. In EnvironmentallySignificant Consumption: Research Directions,ed-ited by P. Stern et al. Washington, DC: Commit-tee on the Human Dimensions of Global Change, National Research Counci l.

Dietz, T. and E. Rosa. 1998. Climate change and soci-ety: Speculation, construction and scientific in-vestigation. International Sociology13(4): 421 455.

Ehrlich, P. and J. Holdren. 1971. Impact of populationgrowth. Science 171: 1212 1217.

Ehrlich, P. and J. Holdren. 1972a. Impact of popula-tion growth. In Population, Resources, and the En-vironment, edited by R.G. Riker. Washington DC:U.S. Government Printing Office. pp. 365 377.

Ehrlich, P. and J. Holdren. 1972b. A bulletin dialogueon the Closing Circle : Critique: One dimen-sional ecology. Bulletin of the Atomic Scientists28(5): 16 27.

Ehrlich, P. and A. Ehrlich. 1990. The population explo-sion. New York: Simon and Schuster.

Factor 10 Club. 1994. Carnoules declaration.Wuppertal, Germany: Wuppertal Institute forClimate, Environment and Energy.

Florida, R. 1996. Lean and green: The move to envi-ronmentally conscious manufacturing. CaliforniaManagement Review 39(1): 80 105.

Freeman, C. 1982. The economics of industrial innova-tion. Cambridge, MA: MIT Press.

Graedel, T. and B. Allenby. 1995. Industrial ecology.

Englewood Cliffs, NJ: Prentice Hall.Graedel, T. 2000. The evolution of industrial ecology.Environmental Science & Technology34(1): 28 31.

Greening, L., W. B. Davis, and L. Schipper. 1998. De-composition of aggregate carbon intensity forthe manufacturing sector: Comparison of declin-ing trends from 10 OECD countries for the pe-riod 1971 1991. Energy Economics20: 4365.

Griliches, Z. 1996. The discovery of the residual: ahistorical note. Journal of Economic Literature34(3): 1324 1330.

8/14/2019 jiec_4_4_13_0

16/17

F O R U M


Grubler, A. 2001. Personal communication.Gurer N. and J. Ban. 1997. Factors affecting energy

related CO 2 emissions: Past levels and presenttrends. OPEC Review XXI(4): 309 350.

Hajer, M. 1996. Ecological modernisation as culturalpolitics. In Risk, environment & modernity: To-wards a new ecology, edited by Scott Lash et al.London: Sage Publications.

Heaton, G., R. Repetto, and R. Sobin. 1991. Trans- forming technology: An agenda for environmentallysustainable growth in the 21st century. Washing-ton, DC: World Resources Institute.

Holdren, J. and P. Ehrlich. 1974. Human populationand the global environment. American Scient ist62: 282292.

Holdren, J. 2000. Environmental degradation: popu-lation, affluence, technology, and sociopoliticalfactors. Environment 42(6): 4 5.

Hosier, R. 1996. Economic development and the en-vironment: Beyond trade-offs. Lecture at YaleUniversity.

Intergovernmental Panel on Climate Change. 1996.Second assessment. Cambridge, UK: CambridgeUniversity Press.

Kates, R. 1997. Population, technology, and the hu-man environment: A thread through time. InTechnological Trajectories and the Human Environ-ment, edited by J. Ausubel and H. Langford.Washington, DC: National Academy Press. pp.3355.

Lifset, R. 1997. A metaphor, a field and a journal. Journal of Industrial Ecology 1(1): 1 3.

Lynn, W. 1989. Engineering our way out of endlessenvironmental crises. In Technology and Environ-ment, edited by J. H. Ausubel et. al. and H. E.Sladovich. National Academy of Engineering,Washington, DC: National Academy Press.

Marchetti, C. , P. S. Meyer, and J. H. Ausubel. 1996.Human population dynamic revisited with thelogistic model: How much can be modeled andpredicted ? Technological Forecasting and SocialChange 52: 130.

Marx, L. 1994. The environment and the Two cul-

tures divide. In Science, Technology and the Envi-ronment, edited by J. R. Fleming et al. and H. A.Gemery. Akron, Ohio: The University of AkronPress, pp. 321.

McDonough, W. and M. Braungart. 1998. The NEXTIndustrial revolution. The Atlantic Monthly. Oc-tober. pp. 82 92.

Meadows, D. , D. Meadows, and J. Randers. 1992. Be-yond the limits: Confronting a global collapse, envi-sioning a sustainable future. Post Mills, VT:Chelsea-Green.

Meyer, W. B. and B. L. Turner II. 1992. Human popu-lation growth and land-use/cover change. An-nual Review of Ecological Systems 23:3961.

Miller, G. T., Jr. 1994. Living in the environment prin-ciples, connections, and solutions, eighth edition.Belmont, California; Wadsworth PublishingCompany.

Mol, A. and D. Sonnenfeld. 2000. Ecological mod-ernization around the world: an introduction.Environmental Politics9(1): 3 16.

National Advisory Council for Environmental Policyand Technology (NACEPT), Report of theTechnology Innovation and Economics Com-mittee (TIE). 1991. Permitting and compliancepolicy: Barriers to U.S. environmental technol-ogy innovation. Washington, DC: U.S. Envi-ronmental Protection Agency.

Reijnders, L. 1998. The Factor X debate: Setting tar-gets for eco-efficiency. Journal of Industrial Ecol-ogy2(1): 13 22.

Rothman, D. and S. deBruyn. 1998. Probing into theenvironmental Kuznets curve hypothesis. Eco-logical Economics25: 143145.

Samuelson, P. and W. Nordhaus. 1998. Economics, six-teenth edition. Boston: Irwin/McGraw-Hill.

Schmidheiny, S. and F. Zorraquin. 1996. Financing change: the financial community, eco-efficiency,and sustainable development. Cambridge, Massa-chusetts: MIT Press.

Simon, J. 1980. Resources, population, environment:An oversupply of false bad news.Science 208:14311437

Simon, J. 1981. Environmental disruption or environ-mental improvement? Social Science Quarterly 62(1): 30 43.

Smith, B. L. R. 1990. American scie nce poli cy sinceWorld War II . Washington, DC: The BrookingsInstitution.

Speth, J. 1988. The greening of technology. TheWashington Post. November 20.

Speth, J. 1990. Needed: An environmental revolution intechnology. A background paper prepared for asymposium: Toward 2000: Environment, tech-

nology and the new century. World ResourcesInstitute: June 13 15.Speth, J. 1991. EPA must help lead an environmental

revolution in technology. Environmental Law.Vol. 21: 1425 1460.

Spiegel-Rosing, I. and D. de Solla Price, eds. 1977.Science, technology, and society: A cross-disciplin-ary perspective. London and Beverly Hills: SagePublications.

Stern, P., C. T. Deitz, V. Ruttan, R. Socolow, and J.Sweeney, eds. 1997. Environmentally significant

8/14/2019 jiec_4_4_13_0

17/17

Ch Th IPAT E i d I V i 29

F O R U M

consumption: Research directions.Washington,DC: Committee on the Human Dimensions of Global Change, National Research Council.

Stoneman, P. 1987. The economic analysis of technology policy. Oxford: Clarendon Press.

Turner, B. L. 1996. Class notes, June.von Weizs cker, E., A. B. Lovins, and L. Lovins. 1997.

Factor Four: Doubling wealth, halving resource use.London: Earthscan Publications Ltd.

U.S. Department of Commerce. 1998. The U.S. envi-ronmental industry. Office of Technology Policy.October.

Wernick, I., P. Waggoner, and J. Ausubel. 1997.Searching for leverage to conserve forests. Jour-nal of Industrial Ecology 1(3): 125 145.

World Commission on Environment and Develop-ment. 1987. Our common future. Oxford: OxfordUniversity Press.

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