Migration, Migration, Population Population Mr. A Mr. A

South High 252South High 252

Ravenstein's Migration Ravenstein's Migration Laws 1870's-1880'sLaws 1870's-1880's

(Still relevant today)(Still relevant today) Most migrants go only a short distance Most migrants go only a short distance

(gravity law) (gravity law) Longer-distance migration favors big-city Longer-distance migration favors big-city

destinations destinations Most migration is rural to urban SMost migration is rural to urban S Each migration flow produces a counter Each migration flow produces a counter

flow (i.e. return to place of birth) flow (i.e. return to place of birth) Most migrants are adults--families are less Most migrants are adults--families are less

likely to make international moves likely to make international moves

Thomas MalthusThomas Malthus

1766-1834.1766-1834. Wrote ‘An essay in the First Principle of Wrote ‘An essay in the First Principle of

population’ first published in 1798population’ first published in 1798 Debatable whether the principles of Malthus Debatable whether the principles of Malthus

two hundred years ago (two hundred years ago (that were very that were very revolutionary and controversialrevolutionary and controversial) have any ) have any relevance to the modern world.relevance to the modern world.

The world population in 1798 was overThe world population in 1798 was over nine hundred million people. We have now nine hundred million people. We have now

passed the six billion mark.passed the six billion mark.

The Core Principles of The Core Principles of Malthus:Malthus:

¤ Food is necessary for human existenceFood is necessary for human existence¤ Human population tends to grow faster than Human population tends to grow faster than

the power on the earth to produce subsistence.the power on the earth to produce subsistence.¤ The effects of these two unequal powers must The effects of these two unequal powers must

be kept equalbe kept equal¤ Since humans tend not to limit their population Since humans tend not to limit their population

size voluntarily - “preventive checks” will size voluntarily - “preventive checks” will control population.control population.

Malthus recognised that population if Malthus recognised that population if unchecked, grows at a geometric rate:unchecked, grows at a geometric rate:

11 2 2 4 4 8 8 16 16 3232

However, food only increases at an However, food only increases at an arithmetic rate, as land is finite.arithmetic rate, as land is finite.

1 2 3 4 5 6 1 2 3 4 5 6

and therefore he said….and therefore he said….

War, famine, disease.

Malthusian Catastrophe

TIME

food population

CHECKSCHECKS

Malthus suggested that once this ceiling Malthus suggested that once this ceiling (catastrophe) had been reached, further (catastrophe) had been reached, further growth in population would be prevented growth in population would be prevented by negative and positive checks. He saw by negative and positive checks. He saw the checks as a natural method of the checks as a natural method of population control. population control.

Negative checks (decreased Negative checks (decreased birth rate)….birth rate)….

Negative Checks were used to limit the Negative Checks were used to limit the population growth. It included abstinence/ population growth. It included abstinence/ postponement of marriage which lowered the postponement of marriage which lowered the fertility rate.fertility rate.

Malthus favored moral restraint (including late Malthus favored moral restraint (including late marriage and sexual abstinence) as a check on marriage and sexual abstinence) as a check on population growth. However, it is worth noting population growth. However, it is worth noting that Malthus proposed this only for the working that Malthus proposed this only for the working and poor classes!and poor classes!

Positive checks (increased Positive checks (increased death rate)death rate)

Positive ChecksPositive Checks were ways to reduce were ways to reduce population size by events such as population size by events such as famine, disease, war - increasing the famine, disease, war - increasing the mortality rate and reducing life mortality rate and reducing life expectancy.expectancy.

'J' Curve - Population Crash 'J' Curve - Population Crash ModelModel

Was he right?Was he right?

Technological improvements which he Technological improvements which he could not have foreseen have taken could not have foreseen have taken place.place.

Increased amount of cropland due to Increased amount of cropland due to irrigationirrigation

Reduced population growth as countries Reduced population growth as countries move through the DTMmove through the DTM