An Analysis of Secured Debt

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Journal of Financial Economics 14 (1985) 501-521. North-Holland

AN ANALYSIS OF SECURED DEBT

Rent M. STULZThe Ohio Srate Lnroer.si v, Columhu~. OlfI, 43210, LISA

Herb JOHNSONUniversrty of Cdifornia, Daols. CA YShl6, tiSA

Received May 1983. final version received March 19X5This paper analyzes the pricing of two types of secured debt and shows that secured debt can beused to increase the value of the firm. In particular, it is shown that some profitable projects willnot be undertaken by a firm which can use only equity or unsecured debt to finance them but willbe undertaken if they can be financed with secured debt. Secured debt is priced for a firm with twoassets and some unsecured debt outstanding. The pricing results are used to illustrate the benefitsof the security provision of secured debt.

1. IntroductionThe use of provisions which give specified creditors priority over the

proceeds of the sale of some asset in the evtnt of bankruptcy or liquidation isextremely widespread. Such security provisions are used, for instance, inproject financing, home mortgages and mortgage bonds, equipment trustcertificates, leases, short-term loans to corporations (for instance, inventoryloans) and most personal loans. However, the pricing of debt which includes asecurity provision (henceforth called secured debt) has not been studiedsystematically and, as argued by Schwartz (1981), the extant literature lacksconvincing explanations for the use of security provisions. Furthermore, noexplanation has been advanced for the fact that firms generally retain in bondindentures the option of financing new projects with secured debt.

*Rene Stulz is grateful for financial support from the Managerial Economics Research Center,University of Rochester. The work on this paper was started while Rem? Stulz was at theUniversity of Rochester and Herb Johnson was at the Louisiana State University. We are gratefulfor useful comments from Cliff Ball, Jim Booth. Harry DeAngelo, John Long, Ron Masulis. StewMyers (a referee). Jerry Warner. and an anonymous referee: for computer assistance from HoYang and B.M. Miller; and especially for useful discussions with and comments from Cliff Smith.We also thank the participants in seminars at Harvard University, Louisiana State University,Ohio State University, University of Rochester, Duke University, University of Michigan andPurdue University.

See ABF (1971, sec. 10-10. in particular pp. 359-360) for a discussion of the relevant bondcovenant. This covenant constitutes a notable exception to the me-first rules discussed inFama-Miller (1972).

0304-405X/85/ 3.30: 198.5, Elsevier Science Publishers B.V. (North-Holland)


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502 R.M. Stub und H. Johnson, An ana ysis of secured debt

This paper provides an analysis of the properties of secured debt and showshow these properties can explain the existence of secured debt. First, we lookat the pricing of secured debt using the contingent-claims pricing techniquesdeveloped by Black-&holes (1973) and Merton (1973, 1974).2 Secured debtcan exhibit some surprising features. It is shown, in particular, that the value ofsecured debt can increase if the standard deviation of the rate of return of thecollateral or of the other assets held by the firm increases. Second, we use thepricing results to provide an analysis of when a firm will find it more attractiveto raise funds with an issue of secured debt than with some other financinginstrument. We demonstrate that it is possible that a firm will undertake aprofitable project if it can finance it with secured debt, but that it will notundertake it if it has to finance it by raising additional equity or by issuingunsecured debt. Furthermore, we show that in general the existing bondholdersare made better off if the firm undertakes a new project and finances it partlywith secured debt, which helps to explain why firms generally retain in bondindentures the option to finance new projects with secured debt. We alsodiscuss how the use of secured debt reduces the monitoring costs of debt.

Throughout most of the paper we focus on pricing secured debt when thefirm also has some other debt outstanding. In the event of default, the othercreditors of the firm can have a rank either equal to or higher than the rank ofthe secured creditors over the proceeds of the sale of the assets not used ascollateral. The existence of other potential creditors, besides the securedcreditors, is necessary to make the pricing problem interesting. If the only debtcurrently issued by the firm is the secured debt, the payoff of the secured debtin liquidation does not differ from the payoff of unsecured debt. The existenceof some other form of debt is also crucial for our analysis of the use of secureddebt by firms. Secured debt is a form of debt which allows shareholders to sellclaims to some payoffs of a new project which otherwise would accrue to theexisting creditors of the firm. It follows that issuing secured debt, compared toissuing other forms of debt, decreases the benefits which accrue to existingbondholders and increases the benefits which accrue to shareholders from theadoption of a new project, thereby making it more attractive for shareholdersto undertake the project.

Our analysis of why firms issue secured debt can be used to explain the useof other financing instruments. For instance, Smith-Wakeman (1985) showhow this analysis applies to the use of financial leases. Furthermore, Mian(1984) points out that setting up a captive financing subsidiary to issue debt issimilar to issuing secured debt.

*Existing results about secured debt differ according to the assumptions made about thedistributions of the two assets, Scott (1977) and Smith (1980) assume the returns are perfectlycorrelated. Stub (1982) assumes that the value of the firm and of the collateral follow lognormaldistributions. which implies that the asset not used as collateral can take negative values andsatisfies a distribution which is difficult to characterize and unlikely to obtain in practice.


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Most of the analysis in this paper assumes that the firm owns two assets withreturns that accrue only in the form of capital gains. In section 2, we derivedistribution-free comparative statics results. In section 3, we obtain compara-tive statics results when both assets held by the firm follow a lognormaldistribution. Section 4 discusses how the use of secured debt can reducemonitoring costs and provides an analysis of how secured debt financingmitigates the underinvestment problem. Section 5 discusses possible extensionsof our work and provides a summary of the results.2. Preliminary results

In this section, we first present the framework used throughout this paper forthe valuation of secured debt. Next, we define formally the payoff function forthe two types of secured debt analyzed in this paper. We also present somedistribution-free results which make it possible to understand better thepayoffs to secured debtholders.2. I. Assumptions and notation

The firm considered here owns two assets, A and B, with values A t) andB(t). In the following. it is assumed that asset B is used as collateral. All debtof the firm has the same maturity T and pays nothing until maturity.3 The firmpays no dividends until date T, when it pays a liquidating dividend. Atmaturity, if B(T) is smaller than the face value F of the secured debt, thesecured bondholders get B(T) plus a claim on A(T); otherwise, they simplyreceive F. The debt of the firm which is not secured by asset B may or may nothave a prior claim on asset A. The debt which is not secured by asset B, calledthe unsecured debt (even though it may be equivalent to secured debt with Aas collateral), has a face value equal to H. The secured debt is called juniorsecured debt with value IV t), if the other debt has a prior claim on asset A,and senior secured debt with value DS t), if its claim on asset A for theresidual is equal to that of the unsecured debt.

It is assumed throughout the paper that:A.l. Markets for traded assets are perfect, i.e., there are no taxes, no transac-

tion costs, no limits on short sales and all investors are price-takers.A.2. There exist unlimited lending and borrowing at the constant rate of

interest R per unit of time.A more general treatment would permit the tWo debt issues to mature at different times. In thiscas, it would be possible to study the effect of an increase in the time to maturity of the secured

debt while keeping the time to maturity of the unsecured debt constant. In this more complicatedsetting, it would be possible for the unsecured debt to be less risky if it matured first. See Geskc(1977) and Geske-Johnson (lYX4) for the valuation of Junior debt when it mature5 at a differentdate from senior debt. and see Jcnacn-Smith (19P5) for a discussion of the incentive problemwhich arise& when the JLI~ICY d t matures ht.


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504 R.M. St& and H. Johnson, An unu ys~s ofsecured debtA.3. A(r) and B(t) cannot take negative values. Furthermore, the joint

distribution of the rates of return of A(t) and B(t) is not affected by achange in A(t) or B(t).

A.4. Markets are complete in the sense that it is possible to construct aportfolio which pays nothing until date T and A(T) at time T and aportfolio which pays nothing until date T and B(T) at time T.

AS. Priority rules are observed exactly in the event of default.4With these assumptions, the value of the firm at time t, V t), is equal to thevalue of its assets, A(t) + B(t). If it is possible to construct a portfolio whichpays V(T) at time T by investing in the two types of debt of the firm and itscommon stock, assumption A.4 is satisfied if there exists either a portfoliowhich pays A(T) or a portfolio which pays B(T) at time T. One would expectthe collateral to be a tradeable asset, which makes assumption A.4 lessrestrictive than it seems.

2.2. ResultsIt follows from the definition of junior secured debt that

DJ(T)=min{B(T)+max(A(T)-H,O),F}. 0)

To obtain distribution-free results, it is useful to create an artificial asset Qwhich pays nothing until date T and pays B(T) + max{ A(T) - H , 0} at date T.Let Q( A, B, H, T - t ) be the current value of asset Q. Define C( x, K, T - t)x(P(x, K, T - t )) to be the current value of a European call (put) option onasset x with exercise price K and maturity at date T. It immediately followsthat

Q(A,B,H,T-~)=B(~)+c(A,H,T-t), (2)so that the current value of asset Q is equal to the sum of the value of asset Bplus the value of a call option on asset A.

The current value of an asset which pays DJ(T) at date T, writtenDJ( A , B, H , F, T - t ), can be expressed as a function of the current value of

4Warner (1977) shows that the courts do not uphold priority rules rigorously. In the event of areorganization, the courts generally issue new claims. The secured creditors receive claims the facevalue of which is equal to the value of the secured debt. However, the true value of the claimsreceived by the secured creditors is smaller than the value of their claim against the assets of thefirm. Whereas the evidence shows that secured creditors benefit from having obtained collateral,the pricing results of this paper are likely to overstate the value of secured debt. Nevertheless, onewould not expect the qualitative rest&s of this paper to be affected by the fact that priority rulesare not observed rigorously by the courts.


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asset Q:DJ(A, B, H, F, T- t) = FemRcTp)- P(Q, F, T- 2). (3)

Eq. (3) shows that the current value of junior secured debt is equal to thecurrent value of a default-free discount bond which matures at the same dateas the secured debt minus the value of a European put option on asset Q. Wecan therefore obtain comparative statics results using the distribution-freeresults of Merton (1973):

aDJ/aA = -P& bQ,aA) > 0, (da)

dDJ/dB = - Pp( dQ/aB) > 0, (4b)aDJ/aF= epRcTp- P,> 0, (4c)aDJ/aH = - Pp( aQ/aH) < 0. (4d)

These results state that the value of junior secured debt increases if the value ofthe assets owned by the firm increases or if the face value of the secured debtincreases, and falls if the face value of the unsecured debt increases. Theintuition for the first three results is the same as the intuition for the pricing ofunsecured bonds and does not need to be repeated here.5 The fourth result,i.e., that the value of secured debt is a decreasing function of the face value ofthe unsecured debt, is explained by the fact that a higher face value for theunsecured debt implies a decrease in the amount from the sale of asset A leftto pay the secured creditors in each state of the world.

Differentiating eq. (3) completely with respect to time t and using put-callparity, we get

am/at = at/at po( aQ/ at . 5)Eq. (5) shows that a decrease in time to maturity has an ambiguous effect onthe value of junior secured debt. If time to maturity decreases while Q is keptconstant, the decrease in time to maturity unambiguously increases the valueof secured debt. However, the value of secured debt is equal to the value of adefault-free discount bond minus the value of a put option on Q. As time tomaturity decreases, the value of Q falls because it is the sum of the value ofasset B plus the value of a call option on asset A. If Q falls sufficiently as timeto maturity decreases, the value of secured debt can fall as time to maturitydecreases. To understand this. notice that if the value of the collateral is small

5See Merton 1974).


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506 R. M . St ul z and H. Johnson, An anal ysysu f secured debtrelative to the face value of the secured bond and if the value of asset Aexceeds the value of the collateral, the secured bond is very much like asubordinated bond.6 The fact that secured debt can behave like subordinateddebt implies that if B(t) is small compared to A(t) and F, and A(t) + B(t) issmaller than the current value of a default-free bond which pays F + H at timeT, junior secured debt is likely to have the same characteristics as an equityclaim. With the assumptions made so far, the value of the equity of the firm isequal to the value of a call option with exercise price equal to the face value ofthe debt and with maturity at date T. The value of the equity of the firm is,consequently, an increasing function of time to maturity. A similar result canbe obtained for an increase in the interest rate R.

If, in the event of bankruptcy, the secured creditors rank equally with theother creditors for the fraction of their claims which is not paid by theproceeds of the sale of the collateral, then we have senior secured debt andthe payoff at maturity of this type of secured debt is given by

DS A, B, H, F, T)i

max(F- B(T),O)max(F- B(T),O) + H (6)

It follows that the payoff of secured debt is again equal to the payoff of adefault-free bond minus the payoff of a put option. In this case, the presentvalue of the risky asset on which the put is written cannot be expressed as thesum of the present values of risky assets with properties that are well-known.However, by taking partial derivatives of the payoff of senior secured debt atmaturity, it can be verified that this payoff is an increasing function of A andB in bankruptcy states and is a non-decreasing function of A and B in theother states. Hence, an increase in A(t) or B(t) increases the value of seniorsecured debt. If the secured debt is a risky asset, an increase in H decreases thepayoff of secured debt in some states of the world. Consequently,DS( A, B, H, F, T - t) is a decreasing function of the face value of the un-secured debt. Furthermore, an increase in the face value of secured debtincreases its value.

It is not possible to obtain results about the effect on the price of secureddebt of changes in some measure of risk of assets A and B without makingassumptions which restrict preferences or the joint distribution of A(T) andB(T). Even with such restrictions, one generally obtains ambiguous resultsbecause the variance of the rate of return of the firm is not always anincreasing function of the variance of the rate of return of A or of B.

6Black and Cox (1976) show that the value of subordinated debt can be a decreasing function oftime to maturity.


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3. The lognormal caseIn section 2, we were able to derive only a limited number of distribution-free

results about the pricing of secured debt. To get further insights into thedeterminants of the price of secured debt, it is necessary to make assumptionsabout preferences or the joint distribution of the returns of assets A and B. Wepursue here a route which has often been followed in financial economics, aswe maintain the assumptions of section 2 and assume furthermore that A andB are lognormally distributed and that trading takes place continuously. As weare not able to obtain closed-form solutions, we compute numerically valuesfor both types of secured debt. The numerical analysis makes it possible tocompute a large number of comparative statics results which provide usefulinsights into the determinants of the price of senior and junior secured debt,While these results are interesting in their own right, some of them have usefulimplications for our analysis of why secured debt exists. In particular, some ofthe discussion in section 4 relies heavily on the comparative statics of the valueof secured debt with respect to changes in the variance of the return of asset A.We also compute the debt value for both types of secured debt when thesecurity provision is removed, which allows us to find the value of the securityprovision. The value of the security provision of junior and senior secured debtis written VDJ( A, B, F, H, T) and VDS( A, B, F, H, T), respectively. The resultson the value of the security provision will be useful in section 4.

The dynamics for A and B are given bydx/x = pL,dt + u,dz,, x=A,B, (7)

where dz, is the increment of a standard Wiener process. For simplicity it isassumed that A(t) and B(t) are the prices at time t of traded assets which attime T will have the same value as the assets of the firm.

Let I( A, B, F, H, 7) be the value at date t = T- 7 of a self-financingportfolio which satisfies the following boundary condition:

V(A,B, F,H,O)=D.J(A,B, F, H,O), i = 0,= DS(A, B, F, H,O), i= 1. (8)

It can be shown that V(A, B, F, H, T) satisfies the following partial differen-tial equation:

-V;=RV-RV,;A-RV;B

- 3 { V;/,Aa; + V;,B2a,2 + 2V;BABpa,a,}, i=O,l, (9)See. for instance, Stulz (1982) or Johnson (1981)


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51 R. M. Stulr und H. Johnson, An unalysis of secured debt

where p is the instantaneous correlation coefficient between the dynamics of Aand the dynamics of B. We assume that p is a constant. The remainder of thissection describes our numerical solutions to the partial differential eq. (9) forthe boundary conditions at maturity given by eq. (8).Table 1 gives results for various cases, most of which have p = 0.5. In thistable, oa, us, P, R, 7, F, H, A, B have the values 0.2, 0.2, 0.5, 0.15,20,1000,1000,50,50, respectively, unless otherwise stated. Notice that thecurrent value of a default-free bond paying 1000 twenty years from now withR = 0.15 is equal to 49.8. The face value of the debt is chosen to be large tomake it easier to understand how variations in the parameters affect the valueof secured debt. As A and B increase relative to the prices of risk-free bondswith the same terms, i.e., He- and FepR, the debt becomes less risky andchanges in the parameters have less of an impact on the value of secured debt.From section 2, we know that the price of senior secured debt is anincreasing function of the face value of secured debt F and of the prices of Aand B, and a decreasing function of the face value of unsecured debt. In table1, the price of senior secured debt is also a decreasing function of theinstantaneous variance of the returns of A and B, of the instantaneouscorrelation coefficient between the returns of A and B, of the interest rate R,of time to maturity T and of the face value of the unsecured debt H. Numerousother cases were studied numerically. All these cases yielded the same qualita-tive results for the pricing of senior secured debt except for the effect ofincreases in the standard deviation of the return of assets A and B (respec-tively, uA and aa). If u,A/u,B is small (large), it is possible for an increase inuA (ue) to increase the value of senior secured debt when the correlationcoefficient of the returns of A and B is negative and close to minus one. Tounderstand this, notice that the value of equity is equal to the value of a calloption on A + B with an exercise price equal to the sum of the face values ofthe outstanding debt of the firm. An increase in a, (ue) can decrease thevariance of changes in A + B if p is smaller than - a, A/ u B ( - uB B/u, A).As the value of equity is an increasing function of the variance of changes inA + B, it follows that an increase in a, ( uB) can decrease the value of equity. Adecrease in the value of equity must increase the total value of the debt claimsagainst the firm if A + B stays constant. (In addition, however, an increase ina, or uB can increase the value of secured debt at the expense of the unsecuredcreditors). In summary, the sign of the partial derivatives of the value of seniorsecured debt is

+++ - +/-+/----DS = DS( A, B, F, H, uA, ~g, P, R, 4. (10)

A description of the procedure followed to obtain these results is available from the authors.


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In table 1, the comparative statics results for junior secured debt are thesame as those obtained for senior secured debt except for changes in thestandard deviation of the return of A. Starting from a low value an increase inthis standard deviation first increases and then decreases the price of juniorsecured debt. To understand this result, remember that in section 2 we showthat the price of secured debt is a decreasing function of a put option on anartificial asset Q whose price is equal to B(t) + C( A, H, T - t), whereC( A, H, T - t) is the price of a call option on asset A with exercise price Hand maturity at time T. An increase in uA brings about a proportionately largerincrease in C(A, H, T) if u,~ is low than if it is high. For low values of uA, anincrease in C( A, H, 7) due to an increase in uA overwhelms the effect on theprice of secured debt of the increase in the standard deviation of asset Q dueto an increase in uA. If the value of u, is large, an increase in Us does notincrease the price of the call option on A sufficiently to increase the price ofsecured debt. Numerous other cases were studied numerically. It turns out thatif the value of the collateral is small compared to the face value of the secureddebt and compared to the value of A (for instance, A = 500, B = 50 andF = H = lOOO), the value of junior secured debt increases with the standarddeviation of asset A, the interest rate and the time to maturity. These resultsoccur because, when B becomes very small, the price of secured debt becomesalmost equal to the price of a default-free bond with face value F minus theprice of a put option on C( A, H, 7). Furthermore, when the standard deviationof price changes of B is small compared to the standard deviation of pricechanges of A and when the correlation coefficient between the returns of A andB is negative and close to minus one, it is possible for increases in the standarddeviation of the return of asset B to decrease the standard deviation of thereturn of asset Q and hence increase the value of secured debt. (For instance, ifA = 1000, B = 50, uA = 0.4, F = H = 1000, p = -0.9, an increase in us from0.3 to 0.35 increases the value of junior secured debt.) In summary, the sign ofthe partial derivatives of the value of junior secured debt is

+ + + - +/- +/- - +/- +/-DJ=DJ(A,B.F,H, a/,, uB, p, R, 7). (11)

Finally, inspection of table 1 shows that the value of the security provision isalways positive for both types of secured debt. This result is not surprising, asthe security provision enables secured creditors to have a bigger claim on theasset used as collateral then they would have in the absence of that provision.It can be shown that this result holds irrespective of the joint distribution ofthe returns of assets A and B. The comparative statics of the value of thesecurity provision will be discussed in section 4.


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512 R M Stulz und H. Johnson, A n mu s of secured dehl4 Why does secured debt exist?4 1 Secured debt theories and the value of the firm

In a recent review of theories explaining the existence of secured debt,Schwartz (1981, p. 3) concludes that efficiency explanations for why firmsissue secured debt either predict wrongly when it will or will not be sold, fail toaccount for the use of security rather than other contractual devices thatapparently accomplish the same ends, or fail to show that security reduces netsocial costs. In other words, existing theories do not convincingly demonstratethat the use of secured debt increases the value of the firm rather thanredistributing the value of the firm among various claimholders. Furthermore,the current literature does not explain why firms retain in bond indentures theoption to finance new projects with secured debt.

In this section, we show how secured debt can be used to increase the valueof a firm. We divide our analysis into two parts. First, we discuss how thesecurity provision can decrease the monitoring costs of debt. Then, we showthat the possibility of financing new projects with secured debt makes it moreadvantageous for a firms shareholders to undertake positive net present value(NPV) projects when the firm has risky debt outstanding.

Before turning to our analysis of the use of secured debt, we want to pointout that a viable theory of the use of secured debt cannot focus merely on theredistribution of wealth among claimholders for a given investment policy ofthe firm. Unexpectedly issuing secured debt (or, for that matter, any kind ofsenior debt) without changing a firms investment policy reduces the valueof the firms existing debt and increases the shareholders wealth. One wouldexpect existing creditors to anticipate the issue of secured debt and to protectthemselves ex ante by requiring a higher yield on the debt when they becomecreditors. As issuing secured debt is costly, the firm is likely to find itadvantageous to pre-commit itself not to issue secured debt for a giveninvestment policy.

4.2. Secured debt and monitoring costsAs argued by Jensen-Meckling (1976) and others, debt involves agency

costs which arise because of the conflict of interest between shareholders andbondholders. To reduce these agency costs, shareholders generally find itadvantageous to attach various covenants to debt issues. Without these cove-nants, creditors would require a higher yield on bonds. For bond covenants to

Smith-Warner (1979a) make this point in their comment on Scotts (1977) argument for the useof secured debt.See Galai-Masulis (1976), Myers (1977), Fama (1978) and Smith-Warner (1979b).


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R.M. St& and H. Johnson, An unu w~s of ecuredehr 513have value, they have to be respected by the firm. Consequently, bondholdersmust spend resources to monitor the firms observance of these bond cove-nants. As these monitoring costs are forecast by potential bondholders andreflected in the prices they are willing to pay for the debt when issued,stockholders have strong incentives to choose efficient combinations of bondcovenants.

Jensen-Meckling (1976) argue that shareholders can reduce the value of thefirms bonds by engaging in asset substitution i.e., by substituting riskier assetsfor less risky ones. With the distributional assumptions of section 3, the valueof the debt falls if the variance of the rate of change of the value of the firmincreases. Bond covenants which specify carefully the firms investment deci-sions would prevent asset substitution. However, such covenants would beexpensive to monitor and would make it difficult for managers to adjust thefirms production and investment plans. Smith-Warner (1979a) andJackson-Kronman (1979) argue therefore that secured debt offers a way tolimit asset substitution which is not as expensive to monitor as alternativeforms of bond covenants which achieve the same end. Of course, this requiresthat suitable collateral be available.

The security provision prevents the firm from selling the collateral to pay adividend or from exchanging the collateral for a more risky asset. This featureof secured debt also (partly) protects secured creditors against asset substitu-tions or cash payouts which do not involve the sale or exchange of thecollateral. Fig. 1 shows that the value of secured debt, in the model used insection 3, depends less on the variance of the rate of return of the asset whichis not used as collateral than does the value of unsecured debt which otherwisehas the same characteristics as the secured debt. Notice that if the firm hassome other debt outstanding, the existence of secured creditors does not affectthe firms incentives to engage in cash payouts or asset substitutions, as it canstill act opportunistically to reduce the value of the claims of unsecuredcreditors. This follows from the fact that the value of the firms common stockis given by the value of a call option on A + B with exercise price F + H . Thevalue of the call option does not depend on how claims are split among variouscreditors of the firm. Hence, while issuing secured debt reduces the firmsopportunities to engage in asset substitution, it does not make asset substitu-tion less profitable given that the firm also has unsecured debt.

Whether the firm currently has unsecured debt outstanding or not, however,costs caused by the possibility of asset substitution can be reduced in a numberof ways by attaching a security provision to the debt. First, given the nature ofthe secured creditors claim, it is in their interest to spend fewer resources togather information about the firm in the process of negotiating the loan andthereafter to monitor the firms observance of bond covenants. Second, securedcreditors are likely to agree to less restrictive covenants about what the firmcan or cannot do later on, as the actions of the firm affect those creditors less


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514 R M Stub and FT. Johnson, An analysis ofsecured debtPriceof Debt

36

32

_NDJ:.k 0.30Variance of Asset A

Fig. 1. The effect on junior secured debt (DJ). junior unsecured debt (NDJ). senior secured debt( DS) and senior unsecured debt (NDS) of an increase in the variance of asset A, i.e., the asset of

the firm not used as collateral. The data used for this figure are based on table 1.

DS

NDS

than if their claim were not secured by some collateral. For instance, if the firmissues unsecured instead of secured debt, it might have its investment policyconstrained by bond covenants which prevent it from taking projects it wouldtake in the absence of unsecured debt. Finally, because secured debt is saferthan unsecured debt, secured creditors benefit less from new investmentsundertaken by the firm than unsecured creditors. Therefore, when a firm hasno debt, issuing secured debt instead of some other form of debt makes it lesslikely that the underinvestment problem discussed by Myers (1977) will arise.Obviously, issuing secured debt instead of unsecured debt also has some costsagainst which the benefits just discussed must be weighed by the issuing firm.

The monitoring cost argument for the use of secured debt can help explainwhy security provisions are often included in short-term debt agreements. If asecurity provision is attached to his claim, a creditor does not require as muchinformation about a firm as he otherwise would. Consequently, a security

The fact that secured debt is safer has an obvious advantage in the models with asymmetricinformation explored by Myers-Majluf (1984) and Myers (1984), as in these models firms want toissue the safest claims first. This follows from the fact that agents with different information setswill value safe debt similarly.


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R M tulr un H ohnson n u nu ~ s i s ofsecured ebt 515provision reduces the costs of negotiating a debt agreement. Furthermore,when the collateral is a pool of assets which would be sold anyway by the firm(for instance, receivables or inventories), the security provision makes itsuperfluous to negotiate covenants which prevent the proceeds from the sale ofthese assets from being shunted off to shareholders (or other creditors).

4.3. Secured debt and the underinvestment problem4.3.1. The main argument

In this subsection, we show that the possibility of financing new projectswith secured debt makes it more advantageous for shareholders to undertakepositive net present value projects. That is, secured debt can be used, in somecircumstances, to solve the underinvestment problem analyzed by Myers(1977).

Shareholders can try to avoid the underinvestment problem by financing thenew project with debt. If the debt used is of rank equal to the rank of theexisting debt, the firm will undertake some projects which would be turneddown if they were equity-financed. Nevertheless, some projects will still beturned down unless the firm can issue debt whose value exceeds the financingrequired for the projects. In this case, debt is sold so that shareholders can paythemselves a dividend. However, such an approach implies higher flotationcosts than if the firm issues debt only to finance the expenditures associatedwith the project. Furthermore, in general, bond issues include bond covenantswhich limit dividend payments, so that shareholders can pre-commit them-selves not to siphon money away from the bondholders through dividendpayments. These bond covenants usually require the firm to earn its dividendpayments. An exception to these bond covenants which would allow the firmto issue debt and pay dividends, so that it will take all positive NPV projects,seems to imply prohibitive monitoring costs, as bondholders would want tomake sure that the firm does not use its investment policy to redistributewealth away from the bondholders. Therefore, such an exception wouldamount to requiring that bondholders and shareholders agree on the amountof debt to be issued.

If the monitoring costs are prohibitively high for a bond covenant whichallows shareholders to issue debt so that the firm will accept all positive NPVprojects, shareholders can find other ways to reduce the importance of theunderinvestment problem. For instance, they can engage in asset substitutionor sell assets to pay a dividend. However, these actions are precisely actionsthat shareholders commit themselves not to take through various bond cove-nants so as to reduce the agency costs of debt. If shareholders want to have theoption to engage in these actions when the underinvestment problem arises, itwill be extremely difficult for bondholders to make sure that these actions are


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516 R. M. Slulz and H. Johnson. An unu ysis ojsrcured debt

taken only to alleviate the underinvestment problem, as promised by theshareholders, and not to transfer wealth from bondholders to shareholders.Instead, shareholders could refund the debt. However, if they can pay off theircreditors easily, the underinvestment problem cannot be severe. Finally,shareholders could negotiate a side-payment from the bondholders. In general,one would not expect bondholders and shareholders to reach easily an agree-ment whereby they share the benefits of the new project so that both partiesare better off.i2

Compared to the various ways of solving the underinvestment problem justdiscussed, financing the project with secured debt, when this option is avail-able, often involves lower monitoring and contracting costs. This is especiallytrue if the shareholders would otherwise take the project only if they can issueunsecured debt to pay themselves a dividend. If the firm owns asset A and hasan option to buy asset B at a price lower than its market value, it will purchaseasset f by doing so it increases the wealth of its shareholders. If the firm canfinance the purchase of asset partly by issuing new debt, it is advantageousfor the shareholders to use asset as collateral for the new debt as the securityprovision diverts from the unsecured bondholders some payoffs of assetwhich would otherwise accrue to them. As the new bondholders acquire thedebt at its fair market value, the gains associated with diverting payoffs of asset

away from unsecured bondholders accrue to the shareholders and increasetheir incentives to undertake the project. Therefore, the option to finance newprojects with secured debt can be valuable to the shareholders, as it makes itmore likely that they will accept positive NPV projects.

When shareholders sell unsecured debt, they can include in the bondindenture a covenant which enables them to finance new projects with secureddebt if it is profitable to do so. Such a covenant can increase the likelihood thatshareholders will be able to redistribute wealth after the unsecured debt isissued by diluting the claim of the unsecured creditors. When investors buy theunsecured bond issue, they pay a price which takes into account the actionsthey expect the shareholders to take. Therefore, the additional agency costscreated by including the option to finance new projects with secured debt inthe bond indenture are borne by the shareholders. It is worthwhile for theshareholders to bear these costs if they expect that the acquired option willenable them to take positive NPV projects they would reject otherwise. Thevalue of the option to finance new projects with secured debt depends cruciallyon the nature of the projects which are forecast to become available before thematurity of the unsecured debt. The more likely it is that some positive NPVprojects would be rejected in the absence of this option, the more valuable this

In the absence of contracting costs, it would seem that the incentives mentioned by Fama(1978) are powerful enough to decrease substantially the importance of the conflict betweenbondholders and stockholders.


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R. M. Stulz und H. Johnson. An un+sis of ecured debt 517option is to the shareholders. This option affects the investment policy of thefirm in such a way that including it in the indenture of an issue of unsecureddebt may increase the value of unsecured debt as, in the event of bankruptcyor liquidation, a fraction of the proceeds from the sale of the collateral for thesecured debt may be used to pay off part of the claim of the unsecuredbondholders. In contrast, including in a bonds indenture the right to issuesecured debt without making new investments allows the shareholders toredistribute wealth away from the bondholders and consequently, in general,decreases the price at which the debt can be sold initially. This discussionimplies that the option to finance new projects with secured debt can increasethe value of the claims against the future cash flows of the firm because itaffects the investment policy of the firm.

4.3.2. The cost of the option o ecured debt JinancingTo understand the cost of the option of secured debt financing, we use the

model of sections 2 and 3 to study the effect on the value of the unsecured debtof the firms decision to exercise its option of secured debt financing. Weassume that the firm has one asset in place, A, and has the option to acquireanother asset, B, by investing 1. The only debt the firm currently has isunsecured debt with face value H. The firm liquidates at time T. If the firmacquires the project and finances it (partly) with an issue of secured debt withmaturity T and face value F, the secured debt is priced according to the earlierresults of this paper.

With junior secured debt, the value of the unsecured debt always increaseswhen the firm uses its option of secured debt financing, as the unsecuredcreditors obtain a claim to some payoffs of asset B and lose nothing (providedB cannot take negative values). With senior secured debt, it is possible for theunsecured creditors to be made worse off when the firm exercises its option ofsecured debt financing. To understand this, notice that if the firm defaults andthe value of the collateral is smaller than the face value of the secured debt. i.e.,B(T) < F and A(T) + B(T) < F + H, the secured creditors have a claim onA(T), which implies a decrease in what the unsecured creditors would other-wise receive. Table 1 shows that, when A and B are lognormally distributed,the lower the variance of the rate of return of asset B, the more likely it is thatunsecured bondholders gain with a senior secured debt issue. Numericalanalysis also shows, for the same distributional assumptions, that the value ofthe unsecured debt is an increasing function of the value of asset B and adecreasing function of the coefficient of correlation between the returns ofassets A and B and of the face value of secured debt. For a given face value ofthe secured debt, an increase in the value of asset B corresponds to an increasein the NPV of the project, i.e., B - I, or else to an increase in the equity usedto finance the project.


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518 R. M . St ul z and H . Johnson, An anul ysl s of secured deht

If the unsecured bondholders believe it likely that shareholders will use theoption of secured debt financing for projects which redistribute wealth, theywill price-protect themselves when they purchase the unsecured debt, whichwill worsen the underinvestment problem in the future. Shareholders canreduce the importance of this problem by committing themselves to financeonly a fraction x (0 -C x < 1) of a new project with secured debt. The smaller x,the more likely it is that the value of the unsecured debt is higher with theproject than without it, but also the less likely it is that the project will beundertaken.

4.4. Empirical implicationsThe analysis of this section has established that there are projects such thatboth unsecured bondholders and shareholders benefit if these projects are

undertaken and financed with secured debt, and that these projects would notbe undertaken if they had to be financed otherwise. The fact that it can be inthe interest of existing bondholders to let the firm finance the acquisition ofnew assets with secured debt is generally recognized in bond indentures.Although bond indentures usually prohibit the firm from issuing secured debtwithout new investments, they often allow the firm to use purchase money,mortgages, liens, pledges or security interests up to some percentage of thecost of an asset newly acquired by the firm.13

From the analysis of this section, it is possible to get some idea of when onewould expect secured debt to be used. For a firm, the option of financing newprojects with secured debt is costly because it increases the agency costsassociated with the initial unsecured debt issue. The use of secured debt itself iscostly for several reasons. First, the contracting costs of secured debt can behigher than the contracting costs of unsecured debt. For instance, securityinterests must often be registered. Second, secured debt implies a loss offlexibility for the firm, as it cannot sell the collateral without renegotiating thedebt, which can be difficult. Finally, while the use of secured debt can reducemonitoring costs, as argued earlier in this section, it also involves somemonitoring costs which do not arise in the case of unsecured debt. Forinstance, if a project undertaken by the firm involves the purchase of a largenumber of assets which can be sold without the transfer of an explicit title tothese assets, e.g., typewriters, the monitoring costs specific to secured debt maybe prohibitive.14

As it is expensive for the firm to acquire the option of financing projectswith secured debt, it will purchase this option only if it expects its benefits to

13See footnote 1.14Benjamin (1978) provides an analysis of the advantages and disadvantages of using various

types of goods as collateral.


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be sufficiently large. Thus, the firm will do so only if it is likely that there willbe available sufficient positive NPV projects for which secured debt financingwill be advantageous. In the following, we show when one would expectsecured debt financing to be advantageous. To focus the discussion on the factthat secured debt can be used to reduce the underinvestment problem, weconsider here the case when secured debt has no other ,benefit.

If the existing debt of the firm is not very risky, there cannot be much of anunderinvestment problem and, therefore, one would not expect the firm to usesecured debt. The underinvestment problem is not likely to be serious for highNPV or high risk projects. However, if the existing debt of the Crm is riskyenough and there is a significant underinvestment problem one would expectsecured debt to be used.

Secured debt is more likely to be used, ceterisparibus, the higher the value ofthe security provision, as this provision measures the value of the payoffs of Bwhich, without it, would accrue to the unsecured creditors. Table 1 providesuseful insights into the comparative statics of the value of the securityprovision when assets A and B are lognormally distributed. In particular. table1 shows that the value of the security provision increases if the standarddeviation of the return of the other assets of the firm increases. It follows thatsecured debt is particularly advantageous if the standard deviation of thereturn of the collateral is much lower than the standard deviation of the returnof the remainder of the assets of the firm. This result is consistent with casualempiricism which suggests that assets with low standard deviations of returnsare more frequently used as collateral than other assets. Furthermore, the valueof the security provision is an increasing function of the face value of thesecured debt, the face value of the unsecured debt, calendar time and the rateof interest. These results are explained by the fact that an increase in theprobability of default, ceteris paribus, increases the value of the securityprovision when the distribution of the collateral is left unchanged. Since thevalue of the security provision is a decreasing function of time to maturity, ouranalysis can explain why one often sees short-term secured debt.i5 Since thevalue of the security provision is an increasing function of the face value of theunsecured debt, one would expect secured debt financing to be used moreoften if the firm has a high leverage ratio than otherwise.

5. ConclusionThis paper shows that secured debt can be used to increase the value of the

firm. In particular, it is argued that the availability of secured debt mitigatesthe underinvestment problem. It is shown that if a firm can finance new

5Remember, however, that this result is derived under the assumption that the maturity of bothtypes of debt is the same.


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52 R. M. Slulz und H. Johnson, An ana vsis of secur ed ebt

projects with secured debt, it is likely to undertake some new projects that itwould otherwise reject. Comparative statics and numerical solutions are pro-vided for the pricing of secured debt.

The analysis in this paper could be extended in a number of ways. The typeof secured debt studied could be modified to allow for coupon payments. Thefirm could be allowed to pay dividends. More realistic assumptions could bemade about the firm and about the asset used as collateral. For instance, thefirm could hold options on projects which can be undertaken at a later dateand the exercise policy for these options could be solved for when the debt isvalued. As the firm has debt outstanding, not all positive NPV projects (i.e.,projects for which the option is in-the-money at maturity) will be undertaken.

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provisions all registered issues 1967, and Certain negotiable provisions which may be includedin a particular incorporating indenture (American Bar Foundation, Chicago, IL).

Benjamin, D.K., 1978. The use of collateral to enforce debt contract, Economic Inquiry 16,333-359.

Black, F. and J. Cox, 1976, Valuing corporate securities: Some effects of bond indentureprovisions, Journal of Finance 31, 351-367.

Black, F. and M. Scholes, 1973, The valuation of options and corporate liabilities, Journal ofPolitical Economy 81, 637-659.

Fama, E., 1978. The effects of a firms investment and financing decisions on the welfare of itsstockholders, American Economic Review 68. 272-284.Fama, E.F. and M. Miller, 1972, The theory of finance (Dryden Press, Hinsdale, IL).

Galai, D. and R.W. Masulis, 1976, The option pricing model and the risk factor of stock, Journalof Financial Economics 3, 53-81.

Geske, R.. 1977, The valuation of corporate liabilities as compound options, Journal of Financialand Quantitative Analysis 12, 541-552.

Geske, R. and H.E. Johnson, 1984, The valuation of corporate liabilities as compound options: Acorrection, Journal of Financial and Quantitative Analysis 19, 231-232.Jackson, T.H. and A.T. Kronman. 1979, Secured financing and priorities among creditors, Yale

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Management Science 4, 141-183.Merton, R.C.. 1974, On the pricing of corporate debt: The risk structure of interest rates, Journalof Finance 29, 449-470.Mian, S., 1984, Captive finance companies and alternative policies for financing accounts receiva-

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Documents

An Analysis of Secured Debt