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Annuities and Retirement∗ Eytan Sheshinski, Department of Economics The Hebrew University of Jerusalem First Draft: January 1999 This Version: September 1999 Abstract This paper examines the interaction between the market for an- nuities and retirement and consumption decisions in the presence of lifetime uncertainty. We focus on two aspects of the demand for annu- ities: the timing of annuitization and the information available to the issuers of annuities with regard to purchasers’ survival probabilities. The First-Best is attained by continuous annuitization of savings, with a guaranteed lump-sum payment to beneﬁciaries upon death. Annu- itization of savings at retirement, and a-fortioti no annuitization, are inferior and lead to distortions in retirement and consumption deci- sions. Applying a ‘Stochastic Dominance’ approach, we show how these decisions depend on individuals’ degree of risk aversion. Un- der imperfect information, we analyze Pooling Equilibria and compare them with the First-Best. ∗ This paper was written while I was visiting Princeton University in the Fall of 1998. I wish to thank my colleagues and friends at Princeton for their hospitality. I also wish to acknowledge useful comments received from Kenneth Arrow, Peter Diamond and Sergiu Hart. 1 1 Introduction Retirement plans involve numerous uncertainties. Foremost is the un- certainty with respect to lifetime. Not only is lifetime duration uncertain but, particularly early in life, survival probabilities are diﬃcult to predict. These depend largely on health conditions which only unfold over time. With these uncertainties, lifetime consumption and savings plans depend crucially on the availability of insurance markets. The market most relevant for the length of life uncertainty is the market for annuities. These ﬁnancial instru- ments provide payments to annuity holders starting on a speciﬁed date and contingent on survival.1 By pooling mortality risks of many individuals, issuers of annuities can fully insure against individual lifetime uncertainty. The terms at which annu- ities are oﬀered in competitive markets depend on the information available to issuers. Purchasers belong to one of a number of ‘risk classes’, each con- sisting of individuals with the same survival function. When suppliers can identify the ‘risk class’ to which customers belong, competitive annuity prices diﬀer by ‘risk class’ and a First Best allocation is attained (Yaari, 1965). When information on survival probabilities is private, or only imperfectly available to ﬁrms, annuity prices are based on ‘pooled’ (average) survival rates of several ‘risk classes.’ Pooling leads to adverse selection, that is, an- nuities are purchased primarily by groups with high survival probabilities while those with low survival probability prefer to purchase fewer annuities.2 In extreme cases, some ‘risk classes’ may choose not to purchase any an- nuities. In a Separating Equilibrium of this kind, the actions of individuals reveal (partially or fully) their characteristics (Rothschild and Stiglitz, 1976). Whenever annuity prices are based on pooling of some ‘risk classes’ the al- location is not First Best. These prices imply transfers (‘cross-subsidization’) 1 These are called ‘single annuities.’ ‘Joint annuities’ provide, in addition, speciﬁed payments to spouses or children after the death of the annuity holder. Section 6 below analyzes this type of annuities. 2 Convincing evidence on the diﬀerent mortality probabilities of annuity purchasers compared to the population average is presented in Mitchell, Poterba, Warshawsky, and Brown (1999). 2 across groups and these entail, in turn, distortions in consumption and in re- tirement decisions. The objective of this paper is to explore the interaction between these decisions and the characteristics of the annuity market. At an optimum retirement age, the beneﬁts and costs of a marginal post- ponement of retirement are equal. The instantaneous beneﬁts of such post- ponement are the wage rate times the marginal utility of consumption. The level of consumption depends, in turn, on the structure of the insurance markets, in particular the market for annuities. Costs are the instantaneous disutility of labor. When beneﬁts decrease and costs increase with age, there is a unique optimum retirement age. This paper focuses on the timing of the annuitization of savings. When the purpose of savings is the provision of consumption during retirement whose duration is uncertain, it is most eﬃcient to annuitize savings continu- ously, i.e. to purchase ‘deferred annuities’ which start payments, contingent on survival, upon retirement. Age-dependent annuity prices are cheaper for young purchasers, reﬂecting the probability that the annuity holder may die prior to retirement. Annuitization of savings at retirement is inferior to con- tinuous annuitization (the same amount of cumulative savings yields a lower post-retirement ﬂow of payments), because insurance ﬁrms are not able to pull mortality risks prior to retirement. Consequently, retirement is delayed and consumption during retirement is lower, compared to the First-Best. This assumes that individuals place no (or low) value on non-annuitized as- sets left behind when death occurs before retirement. When individuals have a bequest motive, the First-Best allocation is at- tained with continuous annuitization and a guaranteed lump-sum payment upon death to designated beneﬁciaries (which entails correspondingly lower retirement beneﬁts). Annuitization at retirement leads to excessive (com- pared to the First-Best) accumulation of assets during the working phase, whereby part of these assets is annuitized upon retirement and part is left for bequest. As with no bequest motive, retirement is delayed, post-retirement consumption and bequests are lower, compared to the First-Best. All individuals are shown to purchase some annuities at any price. Hence, no Separating Equilibrium exists. A Pooling Equilibrium distorts consump- tion and retirement decisions. Speciﬁcally, if individuals are suﬃciently risk- 3 averse (coeﬃcient of relative risk aversion larger than one), retirement ages and consumption are ‘pooled’ together compared to the First-Best. It has been argued that annuity markets in the U.S. are expensive and ineﬃcient (e.g. Friedman and Warshawsky (1990), Mitchell, et. al. (1999), Walliser (1998)). It is not clear how much of this ineﬃciency can be at- tributed to the existence of a mandatory Social Security system which pro- vides (real) annuities at pooled rates and leaves little room for residual de- mand. We do not discuss directly the merits of diﬀerent reform proposals for the U.S. Social Security system. Our underlying assumption is that a competitive, decentralized and voluntary annuity market is feasible and we analyze its potential eﬃciency under alternative informational structures. The use of annuities to insure against lifetime uncertainty has been in- troduced by Yaari (1965). A number of papers (Merton (1981), Sheshinski and Weiss (1981), and Abel (1993)) excluded by assumption private annuity markets and focused on insurance oﬀered by the government. The ﬁrst paper that examined the diﬀerent types of annuity market equilibria is Eckstein, Eichenbaum and Peled (1985). The issue of the timing of annuity purchases was analyzed by Brugiavini (1993).3 These papers used a two or three-period model and did not examine endogenous retirement and its interaction with the annuity market. 2 Optimum Consumption and Retirement with Lifetime Uncertainty Consider an individual who has to decide on his or her optimum con- sumption at diﬀerent ages and the age of retirement in the presence of uncer- tainty about the length of life. Suppose that this is the only uncertainty that the individual faces. Later we analyze the eﬀects of additional uncertainties with respect to future income and survival rates. Let T , T > 0, be the planning horizon, i.e. maximum lifetime (it is possible to allow T = ∞). Lifetime uncertainty is represented by a survival 3 I became aware of Brugiavini’s paper and of the timing of annuitization from a lecture note by Peter Diamond. 4 distribution function F (z), which is non-increasing in age, z, 0 ≤ z ≤ T , with F (0) = 1, F (T ) = 0. Denote consumption at age z by c(z), c(z) ≥ 0. Utility of consumption at diﬀerent ages is separable and independent of age and there is no subjective discount rate. Instantaneous utility, u(c), displays risk-aversion (u0 (c) > 0, u00 (c) < 0) and, to ensure an interior solution, satisﬁes the end-conditions u0 (0) = ∞ and u0 (∞) = 0. When working, the individual provides one unit of labor. Disutility of work, a(z) > 0, 0 < z < T , is independent of consumption and nondecreasing with age, a0 (z) ≥ 0. Again, to ensure an interior solution, assume that a(0) = 0 and a(T ) = ∞. Contingent on survival, the individual works between ages 0 and R, 0 < R < T , i.e. retirement occurs at age R. The individual’s objective is to maximize expected utility, V , ZT ZR V = F (z)u(c(z))dz − F (z)a(z)dz. (1) 0 0 The choice of the optimum consumption path and age of retirement will depend on the insurance options available in the market. 2.1 No Annuities Consider ﬁrst the case when no insurance is available. Let wages at age z be w(z), w(z) ≥ 0. Savings, w(z) − c(z), earn a zero rate of interest.4 With no initial assets, the individual’s assets at age z, B(z), are equal to cumulative savings: Zz B(z) = W (z) − c(z)dz, 0 ≤ z ≤ T, (2) 0 4 It is well-known how the results are modiﬁed when the rate of interest and the sub- jective discount rate are positive. 5 R min(z,R) where W (z) = w(z)dz, 0 ≤ z ≤ T , are cumulative wages. Feasible 0 consumption plans must have non-negative assets at all ages:5 B(z) ≥ 0. (3) Maximization of (1) subject to (3) with respect to c(z) and R yields ˆ F.O.C. for an interior solution (ˆ(z),R) c F (z)u0 (ˆ)(z)) − λ = 0, 0 ≤ z ≤ T, c (4) ˆ ˆ a(R) − ψ(R) = 0, (5) where ψ(R) = u0 (ˆ(R))w(R) for all R, 0 < R < T , and λ, λ > 0, is a c constant. Condition (4) indicates that optimum expected marginal utility is constant over age. Denote the solution to (4) by c(z) and write c(z) = c0 h(z), ˆ ˆ 0 where h(0) = 1 and, from (4), u (c0 ) = λ. Optimum consumption is seen to decrease with age, c0 (z) ˆ h0 (z) 1 f (z) = =− , (6) ˆ c(z) h(z) σ F (z) 00 where σ = σ(z) = − uu0(c)c > 0, is the elasticity of the marginal utility, (c) termed Coeﬃcient of Relative Risk Aversion, f (z), f ≥ 0, is the density of f 1 − F (z) and F(z) is the conditional probability of dying at age z, termed the (z) Hazard-Rate. By (4) and the assumption that u0 (0) = ∞, c(T ) = h(T ) = 0. ˆ With no bequest motive, constraint (3) is binding at T . This condition is used to solve for initial consumption, c0 , R R w(z)dz 0 c0 = c0 (R) = (7) RT h(z)dz 0 5 Since optimum consumption is shown below to strictly decrease with age, (3) implies that B(z) > 0, R ≤ z < T . The constraint B(z) ≥ 0 may bind the optimum consumption path for 0 ≤ z < R. 6 The condition which determines the optimum retirement age, (5), has an intuitive interpretation. A marginal postponement of retirement yields an ad- ditional income of w(R). It’s value in utility terms is ψ(R) = u0 (ˆ(R))w(R). c The costs of postponement in utility terms are the disutility of labor, a(R). At the optimum, costs and beneﬁts are equalized. The sign of ψ0 (R) cannot be established in general and hence there is a possibility of multiple solutions to (5).6 An example is provided below. We ˆ shall not dwell on this question and assume a unique solution, denoted R.7 ˆ Optimum expected utility, denoted V , is given by ZT ZR ˆ V = F (z)u(ˆ(z))dz − c F (z)a(z)dz (8) 0 0 2.2 Continuous Annuitization An annuity is a ﬁnancial instrument which promises certain payments at speciﬁed ages, contingent on survival of the holder of the annuity.8 The issue of annuities can promise certain payments by pooling the mortality risks of many individuals. When individuals save in order to ﬁnance consumption during retirement, it is eﬃcient to convert savings continuously during the working phase into annuities which will start payments upon retirement. The purchase of such ‘deferred-annuities’ provides perfect insurance against lifetime uncertainty and the individual takes advantage of the lower prices 6 Diﬀerentiating ψ(R) with respect to R, ψ0 (R) f (R) w(R) w0 (R) = − σ(R) R + ψ(R) F (R) R w(R) w(z)dz 0 7 ˆ ˆ R satisﬁes second order conditions if a(R) − ψ(R) < (>)0 for R < (>) R whenever (5) is satisﬁed. 8 Annuities that also provide payments to beneﬁciaries after the death of the annuity holder are discussed in Section 6. 7 of early annuity purchases which reﬂect the probability that the purchaser does not survive to retirement.9 All individuals are assumed to have the same survival distribution func- tion, F (z). With a zero rate of interest, lending and borrowing is made at a discount rate equal to this common rate. Hence, without loss of generality, we can take annuity payments to be synchronized with consumption during retirement. With continuous conversion of savings, w(z) − c(z), into annuities which start payments at R, competition implies a zero expected proﬁts condition: ZT ZR F (z)c(z)dz − F (z)(w(z) − c(z))dz = 0 R 0 or ZT ZR F (z)c(z)dz − F (z)w(z)dz = 0. (9) 0 0 Maximization of (1) subject to (9) with respect to c(z) and R, yield F.O.C. for an interior solution (c∗ (z), R∗ ): u0 (c∗ (z)) − λ = 0, 0 ≤ z ≤ T (10) a(R∗ ) − φ(R∗ ) = 0 (11) where φ(R) = u0 (c∗ (R))w(R) for all R, 0 ≤ R ≤ T , and λ, λ > 0, is a constant.10 9 Age-dependent prices assume, of course, full infomration on the purchasers age. Pur- chasing deferred annuities is equivalent to investing in a large pension fund which dis- tributes the assets of deceased members to survivors of the same age cohort. 10 The functional form of φ, (11), and ψ, (5), is the same, but their dependence on R diﬀers because of the diﬀerent consumption paths, c∗ (z) and c(z), respectively. We use ˆ thoughout the same notation for the Lagrangan constants, λ, but their values diﬀer, of course, for each maximization. 8 It is seen from (10) that optimum consumption is constant: c∗ (z) = c∗ , 0 ≤ z ≤ T . By (9), for all R, 0 ≤ R ≤ T , W (R) c∗ = c∗ (R) = (12) z R T where z = F (z)dz is life-expectancy,11 and 0 ZR ZR W (R) = F (z)w(z)dz = f (z)W (z)dz + (1 − F (R))W (R). (13) 0 0 is expected total wages until retirement. Condition (11) determines the optimum retirement age, R∗ . As before, it balances the beneﬁts and costs of a marginal postponement in retirement. When w0 (R) ≤ 0, φ(R) decreases with R and (11) determines a unique solution.12 Optimum expected utility, denoted V ∗ , is ZT Z∗ R V ∗ = u(c∗ ) F (z)dz − F (z)a(z)dz = 0 0 µ ¶ Z∗ R W (R∗ ) u z− F (z)a(z)dz. (14) z 0 Fully insuring against lifetime uncertainty, continuous annuitization is the First-Best allocation. Hence, 11 R T R T Integrating by parts: F (z)dz = zf (z)dz where f (z) is the density of 1 − F (z), 0 0 when it exists. 12 For all R, 0 ≤ R ≤ T , φ0 (R) w0 (R) w(R) u00 (c∗ (R))c∗ (R) = − σ(R) F (R), where σ(R) = − >0 φ(R) w(R) W (R) u0 (c∗ (R)) 9 ˆ Proposition 1: V ∗ > V . Proof. By concavity, u(c) < u(c∗ ) + u0 (c∗ )(c − c∗ ), for any (c, c∗ ), c 6= c∗ . Let c = c(z) be a function of z. Multiplying by F (z) and integrating, ZT ZT ∗ F (z)u(c(z))dz < u(c ) F (z)dz 0 0 T Z ZT +u0 (c∗ ) F (z)c(z)dz − c∗ F (z)dz 0 0 ZT ZT ZR = u(c∗ ) F (z)dz + u0 (c∗ ) F (z)c(z)dz − F (z)w(z)dz , (15) 0 0 0 where R corresponds to c∗ = c∗ (R) by (12). Now take c(z) = c(z) and ˆ ˆ ˆ R = R, the optimum with no annuities. Setting w(z) = 0 for R < z ≤ T , Rˆ R R T write F (z)w(z)dz = F (z)w(z)dz. Integrating by parts, using condition 0 0 R T R T Rˆ R (3), F (z)(w(z) − c(z))dz ≥ 0, or ˆ F (z)ˆ(z)dz ≤ c F (z)w(z)dz. It now 0 0 0 follows from (15) that ZT ZT c ˆ F (z)u(ˆ(z))dz < u(c (R)) ∗ F (z)dz. (16) 0 0 Rˆ R Subtracting F (z)a(z)dz on both sides of (16), noting that V ∗ is maximum 0 ˆ at R = R∗ , it follows from (8) and (14) that V < V ∗ . ¥ 10 2.3 Annuitization at Retirement Suppose that savings are converted to annuities only upon retirement.13 The zero expected proﬁts condition is now ZT ZR F (z)c(z)dz − F (R) (w(z) − c(z))dz = 0 (17) R 0 Maximization of (1) subject to (17) yields F.O.C. for an interior solution c ˆ (ˆR (z), RR ): F (z)u0 (ˆR (z)) − λF (R) = 0, c 0≤z≤R (18) u0 (ˆR (z)) − λ = 0, c R<z≤T (19) and ˆ ˆ a(RR ) − φR (RR ) = 0 (20) where φR (R) = u0 (ˆR (R))w(R), for all R, 0 ≤ R ≤ T , and λ, λ > 0, c is a constant. It is seen from (18) and (19) that optimum consumption decreases for 0 ≤ z ≤ R and is constant thereafter (Figure 1). Again, write cR (z) = c0R h(z), 0 ≤ z ≤ R, where h(0) = 1 and, by (18), h(z) satisﬁes ˆ diﬀerential equation (6). Initial consumption, c0R , is solved from (17), R R w(z)dz 0 c0R = c0R (R) = . (21) h(R) R T R R F (R) F (z)dz + h(z)dz R 0 13 This is the case in many of the mandatory privately managed pension schemes, fol- lowing the example of Chile. See Diamond and Valdez-Prieto (1994). Assets of deceased members in each fund are transferred to designated beneﬁciaries. It is assumed here that individuals put on value on these transfers. In Section 6 below, we introduce a bequest motive. 11 ˆ Optimum expected utility with annuitization at retirement, denoted VR , is thus ˆ ZR ZT ZR R ˆ VR = F (z)u(ˆR (z))dz + u(ˆR (R)) c c F (z)dz − F (z)a(z)dz (22) 0 ˆ RR 0 Annuitization at retirement is inferior to continuous annuitization and superior to no annuitization: ˆ ˆ Proposition 2: V ∗ > VR > V . Proof is straightforward. 3 Comparison of Optimum Retirement Ages We want to compare optimum retirement ages and levels of consumption during retirement under the diﬀerent insurance regimes. Without annuities, optimum consumption during retirement decreases with age. In this case, therefore, optimum retirement age is uniquely related only to the level of consumption upon retirement. 3.1 Continuous Annuitization vs. Annuitization at Retirement First, we show that optimum retirement age is lower with continuous annuitization than with annuitization at retirement: ˆ ˆ ˆ Proposition 3: R∗ < RR and c∗ > cR (RR ). ˆ Proof. From conditions (11) and (20) it is seen that R∗ < RR if c∗ (R) > cR (R) for all R, 0 ≤ R ≤ T. >From (3), ˆ ZR ZR F (R) (w(z) − cR (z))dz < ˆ F (z)(w(z) − cR (z))dz ˆ (23) 0 0 12 for all R, 0 ≤ R ≤ T . Hence, by (17) and (24) ZR ZT ZR F (z)ˆR (z)dz + cR (R) c ˆ F (z)dz ≤ F (z)w(z)dz (24) 0 R 0 Since, by (18), cR (z) > cR (R), 0 ≤ z < R, it follows from (24) and (12) that ˆ ˆ R R F (z)w(z)dz ˆ cR (R) < 0 = c∗ (R). ¥ (25) R T F (z)dz 0 This result is intuitive. Without insurance during the working phase and facing decreasing survival rates, the individual chooses decreasing levels of consumption so as to keep expected marginal utility constant. Consequently consumption during retirement is lower than under complete insurance, i.e. continuous annuitization. In the absence of annuitization, consumption is uninsured both before and after retirement. The decision on optimum retirement depends therefore both on the survival distribution function and on the individual’s risk aversion. Before we analyze this case it will be useful for subsequent discussions to link it to the familiar notion of ‘Stochastic Dominance’. 3.2 Ranking of Survival Functions Consider two survival distribution functions, F1 (z) and F2 (z), 0 ≤ z ≤ T . Clearly, Fi (0) = 1, Fi (T ) = 0 and Fi (z) non-increases in z, i = 1, 2. Deﬁnition 1. (‘Single Crossing’ or ‘Stochastic Dominance’): The func- tion F1 (z) is said to (strictly) stochastically dominate F2 (z) if the ‘Hazard- Rates’ satisfy f2 (z) f1 (z) > , 0 ≤ z ≤ T. (26) F2 (z) F1 (z) 13 d`nF (z) In words, the rate of decrease of survival probabilities, dz f = − F(z) , (z) is smaller at all ages with distribution 1 than with 2. Two implications of this deﬁnition are important. First, consider the functions R Fi (z) , 0 ≤ z ≤ T , i = 1, 2. Being positive and their integral over T Fi (z)dz 0 (0, T ) equal to one, they must intersect (cross) at least once over this range. At any such crossing, when R F1 (z) = R F2 (z) , condition (26) implies that T T F1 (z)dz F2 (z)dz 0 0 d T F1 (z) > d T F2 (z) . Hence, there can be only a ‘single crossing’. dz R dz R F1 (z)dz F2 (z)dz 0 0 That is, there exists an age zc , 0 < zc < T , such that (Figure 2), F1 (z) F2 (z) S as z S zc . (27) R T R T F1 (z)dz F2 (z)dz 0 0 Intuitively, (27) means that the dominant distribution has higher (lower) survival rates, relative to life expectancy, at older (younger) ages. Second, since Fi (0) = 1, i = 1, 2, it follows from (27) that ZT ZT z1 = F1 (z)dz > F2 (z)dz = z 2 , (28) 0 0 i.e., stochastic dominance implies higher life expectancy. 3.3 Eﬀects of Annuitization We are now ready to compare the no-annuities case with those where annuitization is available, either continuously or at retirement. With no insurance against lifetime uncertainty, the individual’s consump- tion and retirement plans depend on his or her attitude towards risk, repre- sented by the coeﬃcient of (relative) risk-aversion, σ. 14 ˆ ˆ Proposition 4: If σ ≥ 1 for all z, 0 ≤ z ≤ T , then R∗ < RR < R and ∗ c > cR > c. ˆ ˆ Proof. Recall that with no annuities, optimum consumption is c(z) = ˆ c0 h(z), where c0 is given by (7), h(0) = 1 and h(z) obeys the diﬀerential equation (6). Note that, by (6), if σ = 1 for all z, 0 ≤ z ≤ T , then h(z) = F (z). We now want to show that, when σ > 1, h(z) stochastically dominates F (z). When σ > 1, then by (6), h0 (z) 1 f (z) f (z) =− >− (29) h(z) σ F (z) F (z) Hence, whenever R h(z) = F (z) , (29) implies that d T h(z) > d T F (z) , T R T dz R dz R h(z)dz F (z)dz h(z)dz F (z)dz 0 0 0 0 which, in turn, implies a ‘single-crossing’. Since h(z) is non-increasing, by (7), R R R R w(z)dz h(z)w(z)dz 0 0 c(R) = c0 h(R) = ˆ h(R) < , (30) RT R T h(z)dz h(z)dz 0 0 for all 0 ≤ R ≤ T . An implication of ‘single-crossing’ is that RR T h(z) − T F (z) dz < 0, for all R < T (because, for R = T the integral R R 0 h(z)dz F (z)dz 0 0 is equal to zero and hence, by (27), it is negative for all R < T ). >From (30) and the identity h(z) = F (z) for σ = 1, we conclude that whenever σ ≥ 1 R R R R h(z)w(z)dz F (z)w(z)dz 0 0 ˆ c(R) < ≤ = c∗ (R) (31) R T R T h(z)dz F (z)dz 0 0 15 for all 0 ≤ R ≤ T . Thus, by (5) and (11) ψ(R) > φ(R), 0 ≤ R ≤ T . Since ˆ a0 (R) ≥ 0, it follows from these conditions that R > R∗ . To show that cR (R) > c(R), for all 0 ≤ R ≤ T , compare c0R , given by ˆ ˆ R F (z) T R h(z) T (22), to c0 , given by (7). We see that c0R S c0 as F (R) dz T h(R) dz. By R R (6), if σ ≥ 1, d`nh(z) h0 (z) h0 (z) dz = h(z) = − σ F(z) ≤ − F(z) = 1 f (z) f (z) d`nF (z) dz , or h(R) ≥ F (z) F (R) for all R ≤ z ≤ T. Thus, c0R ≥ c0 (with equality when σ = 1), and the result follows (Figure 3). ¥ 4 Income Eﬀects on Optimum Retirement Write wages at age z as θw(z), where θ, θ > 0, is a constant. A change in θ is a proportionate change in wages at all ages.14 Using (12), (7) and (22), it can be shown that the elasticities of c∗ (R), cR (R) with respect to θ and cR (R) are all equal to one. Furthermore, from ˆ ˆ the deﬁnitions of φ(R), ψ(R), and φR (R), (11), (5) and (20), respectively, it can be shown that θ ∂φ θ ∂ψ θ ∂φR = = =1−σ (32) φ ∂θ ψ ∂θ φR ∂θ ˆ ˆ for all 0 ≤ R ≤ T . Consequently, R∗ , R and RR all decrease (increase) when wages increase provided σ > (<)1. Intuitively, a large coeﬃcient of risk aversion implies that the negative income eﬀect due to increased wages (labor being a normal good) outweighs the positive substitution eﬀect (due to a larger opportunity cost to retire), and vice-versa. 14 In Section 7 we study a more general case, where θ is uncertain and occurs sometime in the future. 16 5 Example Consider the survival function e−αz − e−αT F (z) = , α > 0 a constant, 0 ≤ z ≤ T (33) 1 − e−αT ³ ´ 1 eαT −1−αT Expected lifetime is z = α eαT −1 , which is inversely related to α. 1 The simplest case to explore is when T → ∞ (and z → α ).15 c1−σ Let u(c) = 1−σ , σ 6= 1 or u(c) = `n(c). Assume that w(z) = w, 0 ≤ z ≤ T. With continuous annuitization, it can be calculated from (12) that c∗ (R) = w(1 − e−αR ). 0 With no annuities, by (4) and (7), c(R) = α0 Rwe−α R , where α0 = α . ˆ σ With annuitization at retirement, by (18) and (22), 0 α0 Rwe−α z cR (z) = ˆ ¡ 0 −α ¢ , 0 ≤ z ≤ R 1 + e−α0 R α α and cR (z) = cR (R) for R ≤ z. ˆ ˆ It can be demonstrated that for α0 < α (i.e. σ > 1), we have c∗ (R) > ˆ ˆ cR (R) > c(R) for all R ≥ 0, implying that R∗ < RR < R. ˆ ˆ Notice that when α0 > α (σ < 1), cR (R) < c(R) and hence RR > R. ˆ ˆ ˆ ˆ ∗ It can also be seen that for small σ it is possible that c(R) > c (R), which ˆ ∗ implies that R > R.ˆ For α0 = α, i.e. σ = 1 (u(c) = `nc), then c∗ (R) > cR (R) = c(R) and ˆ ˆ ∗ R <R ˆ ˆ R = R. For this case (Figure 4), φ(R) = w = 1 is the inverse c∗ 1−e−α/R of the ‘replacement-ratio’, i.e., the ratio of post-retirement consumption to pre-retirement income. 15 All subsequent results hold also for ﬁnite T . 17 1 1 ψ(R) = φR (R) = αR eαR , is downward (upward) sloping for R < (>) α . 1 Thus, if it is assumed that retirement age is earlier than life expectancy, α , uniqueness is guaranteed. Comparative statics also yield expected results. For example, for σ = 1 the elasticity of optimum retirement with respect to life expectancy is ∗ αR∗ e−αR α dR∗ 1−e−αR ∗ = R ∗ α0 (R∗ ) ∗ −αR∗ (34) R∗ dα + αR e ∗ α(R∗ ) 1−e−αR d dR∗ Hence, −1 ≤ R∗ dα ≤ 0. 6 Bequest Motive It was assumed above that individuals have no bequest motive. Con- sequently, savings are used solely to ﬁnance consumption during retirement. With continuous annuitization, since all wealth is in the form of (deferred) annuities, no resources are left behind when individuals die. In the absence of a market for annuities, or when savings are annuitized at retirement and death occurs earlier , some resources held to ﬁnance consumption during retirement are left behind when death occurs, their level depending on the age of the deceased. So far, we assumed that individuals’ consumption and retirement plans place no value on these uncertain resources left behind. Suppose now that individuals have a bequest motive, that is, they have a utility, v(B), from assets left behind as bequests B(≥ 0). Consider ﬁrst the complete insurance case, i.e. continuous annuitization of savings with payments, contingent on survival, starting after retirement and, in addition, a certain amount provided to beneﬁciaries upon death.16 16 This is similar to the ‘ﬁxed payments certain’ type of annuities which ensure payments to annuitants’ beneﬁciaries for a ﬁxed period. This annuity, however, does not provide complete insurance if the amount that beneﬁciaries receive depends on the time of death. For a description of the type of annuities available in the U.S. see Poterba (1997). 18 The zero expected proﬁts condition is ZT ZR B+ F (z)u(c(z))dz − F (z)w(z)dz − B0 = 0 (35) 0 0 where B0 is initial endowment. Maximization of expected utility ZT ZR V = F (z)u(c(z))dz − F (x)a(z) + v(B) (36) 0 0 subject to (34) determines optimum consumption, c∗ , retirement age, R∗ , and bequests B ∗ , satisfying F.O.C. u0 (c∗ ) − v 0 (B ∗ ) = 0 (37) a(R∗ ) − u0 (c∗ )w(R∗ ) = 0 (38) and W (R∗ ) + B0 − B ∗ c∗ = (39) z where W (R) is given by (13). Diﬀerentiating (37)-(39), it is seen that con- dc∗ ∗ sumption and bequests are normal goods, dB0 > 0 and 0 < dB0 < 1.17 dB Thus, in a dynamic setting, bequests can be viewed as converging to a ﬁxed-point or steady state, B0 = B ∗ . When savings are annuitized at retirement, the terms of the annuities can again include a certain level of bequests (reﬂected, correspondingly, with a lower level of payments). If however, an individual dies during the working phase, the level of assets left behind depends on the age of death. Expected utility is given by ZT ZR ZR V = F (z)u(c(z))dz − F (z)a(z)dz + f (z)v(B(z))dz + F (R)v(BR ) 0 0 0 (40) 00 ∗ 17 dB ∗ h u (c00) ∗ dB0 = u (c )w(R∗ )2 F (R∗ ) i and, by second-order conditions, a0 (R∗ ) − u00 (c∗ )+v00 (B ∗ ) z− a0 (R∗ )−u0 (c∗ )w0 (R∗ ) u0 (c∗ )w0 (R∗ ) > 0. 19 where BR is the (certain) level of bequest after retirement. The level of assets, B(z), during the working phase is given by (2). Assets change is equal to savings, B 0 (z) = w(z) − c(z), 0≤z≤R (41) with B(0) = B0 . The zero expected proﬁts condition is R ZT Z F (z)c(z)dz − F (R) (w(z) − c(z))dz − BR + B0 = 0. (42) R 0 Maximization of (40) subject to (41) and (42) yields optimum consump- ˆ tion, cR (z), the corresponding path of assets prior to retirement, B(z), 0 ≤ ˆ ˆ ˆ z ≤ R, retirement age, RR , and bequest after retirement, BR . As before, c(z) = c(R), R ≤ z ≤ T , i.e. optimum level of consumption after retirement ˆ ˆ is constant. All the optimum values depend on initial endowment, B0 . We want to compare continuous annuitization with annuitization at re- tirement when both are in a steady-state. That is, when B0 = B ∗ and ˆ B0 = BR , respectively. ˆ Proposition 5. In a steady-state with a bequest motive, R∗ < RR , ˆ cR (R) < c∗ and B R < B ∗ . ˆ Proof. See Appendix A. The comparison of steady states eliminates, as seen for the budget con- straints (35) and (42), income eﬀects. Qualitatively, the previous results are seen to carry-over in the presence of a bequest motive. Of course, without annuitization, lifetime uncertainty makes bequests random at all ages and the appropriate model to analyze optimum consumption and retirement is via the stationary asset distributions generated by bequests.18 18 We plan to analyze this case in a companion paper. 20 7 Lifetime and Income Uncertainty Suppose that individuals face lifetime uncertainty and are also uncertain about their future income. Income uncertainty may reﬂect, for example, the possibility of future disability. It is assumed that income uncertainty cannot be insured, presumably due to ‘Moral-Hazard’. We model income uncertainty by assuming that beyond a certain age M , prior to retirement, wages become θw(z), where θ, θ > 0, is a constant which can assume diﬀerent Rθ values, 0 < θ < θ, with probability p(θ), 0 ≤ p(θ) ≤ 1, i.e. p(θ)dθ = 1. 0 Consumption after the realization of θ (at M ), and the chosen retirement age, depend on θ. Denote these c(θ, z) and R(θ), respectively. Expected utility is now ZM V = F (z)u(c(z))dz + 0 Zθ ZT Z R(θ) p(θ) F (z)u(c(θ, z))dz − F (z)a(z)dz dθ (43) 0 M 0 Under continuous annuitization, a zero expected proﬁts condition holds for each θ, ZM ZT ZM F (z)c(z)dz + F (z)c(θ, z)dz − F (z)w(z)dz − 0 M 0 Z R(θ) θ F (z)w(z)dz = 0, 0 ≤ θ ≤ θ. (44) M Maximization of (43) subject to (44) yields constant optimum consump- tion prior to M , c∗ , and constant optimum consumption after age M depen- dent on θ, c∗ (θ). These contingent optimum consumption levels satisfy the 21 condition, Zθ 0 ∗ u (c ) = p(θ)u0 (c∗ (θ))dθ (45) 0 Optimum marginal utility of consumption prior to M is equal to expected optimum marginal utility of consumption after M . For each θ, optimum retirement, R∗ (θ), is determined by the condition a(R∗ (θ)) − φ(θ, R∗ (θ)) = 0 (46) where for any R, φ(θ, R) = θw(R)u0 (c∗ (θ, R)). The level of c∗ (θ, R) depends on R through (44), R M R R F (z)(w(z) − c∗ )dz + θ F (z)w(z)dz ∗ 0 M c (θ, R) = (47) R T F (z)dz M To ﬁnd the eﬀect of θ, diﬀerentiate φ with respect to θ, given R, θ ∂φ = 1 − σε (48) φ ∂θ where, by (44) and (47), R R θ F (z)w(z)dz θ ∂c∗ (θ, R) M ε= ∗ = M (49) c (θ, R) ∂θ R R R F (z)(w(z) − c∗ )dz + θ F (z)w(z)dz 0 M The eﬀect of θ on φ depends on the product of the coeﬃcient of risk aversion, σ, and the elasticity of optimum consumption after M with respect to θ, ε. The value of ε depends on the timing of the change in wages, M , relative to R. 22 By (47), ε > 0 for all 0 ≤ M ≤ R, ε = 1 when M = 0 and ε = 0 when R M M = R.19 If annuitized savings prior to M are negative, F (z)(w(z) − 0 c∗ )dz < 0 (in expectation of high wages afterward), ε may be larger than 1 for some M (Figure 5a). The eﬀect of θ on φ and, by (46), on the optimum R, is seen to depend on the sign of 1 − σε (Figure 5b). If σ > 1 for all z, then ∂φ < 0 for small ∂θ M and ∂φ > 0 for M close to R. This implies, by (46), that for small (large) ∂θ M , an increase in wages decreases (increases) the optimum retirement age. The explanation is that the earlier the wage increase occurs the larger is the income eﬀect, which, with σ > 1, outweighs the (opposite) substitution eﬀect. When σ < 1 the substitution eﬀect works in the same direction as the income eﬀect to increase optimum retirement age. 8 Diﬀerent ‘Risk Classes’: Full Information Suppose that the population consists of two homogeneous groups, i = 1, 2. Individuals in each group, called ‘risk-class’ by insurance ﬁrms, have the same survival function, Fi (z). Assume that groups 1’s survival function stochastically dominates, ac- cording to (26), that of group 2. In particular, group 1 has a higher life expectancy. Assume further that ﬁrms can identify annuity purchasers according to the group to which they belong. In a perfectly competitive market, annuities are then priced diﬀerently for each group, the analysis in Section 2 applying to each group separately. We focus on the eﬀect of heterogeneity in survival rates and hence assume that wages are the same for both groups. 19 R M In (47), c∗ also depends on M through (46). Furthermore, as M → R, F (z)(w(z) − 0 c∗ )dz > 0 since c∗ (θ, R) → c∗ . The case M = 0 has been discussed in Section 4. 23 Proposition 6: With full information and continuous annuitization, ∗ ∗ R1 > R2 . R R Fi (z)w(z)dz Proof. Applying (12) to each group, c∗ = c∗ (R) = i i 0 R T , i = 1, 2. Fi (z)dz 0 By (27), R R R R F1 (z)w(z)dz F2 (z)w(z)dz 0 0 c∗ (R) 1 = < = c∗ (R), 2 (50) R T R T F1 (z)dz F2 (z)dz 0 0 for all R, 0 < R < T . It follows from (11) that R1 > R∗ . ∗ 2 ¥ Individuals with higher life expectancy partially compensate for longevity by retiring later, but their optimum consumption remains lower throughout. Without insurance, the eﬀect of higher life expectancy on optimum re- tirement is indeterminate. Recall from (7) that R R w(z)dz 0 ci (R) = ˆ hi (R) i = 1, 2 (51) R T hi (z)dz 0 h0 (z) where hi (R) is deﬁned by (6): hi (0) = 1 and i hi (z) 1 f = − σ Fii(z) . It now follows (z) from (27) that h1 (R) h2 (R) S as R S Rc (52) R T R T h1 (z)dz h2 (z)dz 0 0 for some Rc , θ < Rc < T . Recall that the beneﬁt from a marginal postpone- ment of retirement, (5), for a group i individual is ψ i (R) = w(R)u0 (ˆi (R)). c ˆ ˆ ˆ ˆ In view of (51) and (52), if R1 < Rc then R1 > R2 , while if R1 > Rc , then ˆ ˆ R1 < R2 . The explanation of this indeterminacy is as follows. In the absence of insurance and with the same age of retirement, individuals with higher life 24 expectancy consume less at early ages and more at advanced ages, compared to individuals with lower life expectancy. Hence, the beneﬁt from a marginal postponement of retirement is higher for the former group, provided that retirement takes place when their consumption is lower. The opposite holds if retirement occurs when their consumption is higher. This argument is easily demonstrated with the help of a simple case from Section 5. With u(c) = `nc, Fi (z) = e−αi z , i = 1, 2, and w(z) = w, one ﬁnds that ψ i (R) = α1R eαi R . Figure 6 clearly displays the reversal possibility and i the critical switch point, Rc , for these functions. 9 Diﬀerent ‘Risk Classes’: Pooling Equilib- rium Social security systems, pension funds and pension schemes oﬀered by employers, trade-unions and professional organizations oﬀer annuities at prices which are based on the ‘pooling’ of survival rates of annuity purchasers who belong to diﬀerent ‘risk-classes’. Sometimes the non-discriminatory pricing of annuities is due to a legal constraint and often it reﬂects the imperfect information available to insurers on purchasers’ risk characteristics. Presum- ably, the costs of additional information are higher than the beneﬁts from selective pricing. When a variety of annuities are oﬀered in terms of the time pattern of payment (over age), diﬀerent ‘risk classes’ will typically choose diﬀerent annu- ities, thereby potentially revealing their type. However, such ‘self-selection’ is not transparent when individuals purchase annuities from many insurers. Rather than question the feasibility of pooling equilibria, we want to explore their implications. Assume again that the population consists of two groups, such that all in- dividuals who belong to a certain group who have the same survival function. We continue to assume that the survival function of group 1 stochastically dominates, according to (26), that of group 2. The relative size of group 1 in the population is g, 0 < g < 1. 25 Annuity prices are based on a uniform age survival function, G(z), which is a weighted average of the two groups’ survival functions, F1 (z) and F2 (z). Clearly individuals in group 1 beneﬁt from being pooled with the shorter- lived group 2. In contrast, individuals in group 2 pay higher prices than those based on their own survival function. However, it can be shown that they always prefer to annuitize some of their savings (see Appendix B). In par- ticular, with continuous annuitization and the ability to adjust consumption at the pooled rate, group 2 individuals choose to annuitize all their savings. When annuities provide a constant ﬂow of payments and consumption may diﬀer from these payments by using non-annuitized resources, group 2 indi- viduals will choose to have a lump-sum available upon retirement in order to supplement consumption over a certain period after retirement (Appendix B). In any case, there is no Separating Equilibrium, i.e. an equilibrium in which only group 1 individuals purchase annuities. With everybody purchas- ing annuities, the pooled survival function has as weights the relative size of the two groups in the population: G(z) = gF1 (z) + (1 − g)F2 (z) (53) Each group’s annuities satisfy a zero expected proﬁts condition: ZT Zi R G(z)ci (z)dz − G(z)w(z)dz = 0, i = 1, 2, . (54) 0 0 Maximization of expected utility subject to (54) yields F.O.C. for opti- e mum consumption, ei (z), and retirement age, Ri , of group i: c Fi (z)u0 (ci (z)) − λi G(z) = 0 (55) e e e a(Ri ) − φi (Ri ) = 0 (56) e where φi (R) = u0 (ei (R))w(R) for all R, 0 ≤ R ≤ T , and λi , λi > 0, constant. c As before, write ei (z) = c0i hi (z), hi (0) = 1. c Solving for c0i from (54), R R G(z)w(z)dz 0 c0i = c0i (R) = (57) R T G(z)hi (z)dz 0 26 Diﬀerentiating (55), h1 (z) and h2 (z) are seen to satisfy: · ¸ h01 (z) 1 − β f2 (z) f1 (z) = − , (58) h1 (z) σ F2 (z) F1 (z) and · ¸ h02 (z) β f1 (z) f2 (z) = − , (59) h2 (z) σ F1 (z) F2 (z) gF1 (z) gF1 (z) where β = G(z) = gF1 (z)+(1−g)F2 (z) , 0 < β < 1. Since F1 (z) stochastically dominates F2 (z), (58) and (59) show that op- timum consumption of group 1 increases, h01 (z) > 0, while that of group 2 decreases, h02 (z) < 0, 0 ≤ z ≤ T . Pooling distorts retirement decisions compared with the First-Best. Specif- ically, optimum retirement ages of the two groups are ‘pooled together’. Proposition 7: In a Pooling Equilibrium with continuous annuitization, ∗ e ∗ e if σ ≥ 1 for all z, 0 ≤ z ≤ T , then R1 > R1 and R2 < R2 . Proof. By (57), since h01 (z) > 0, R R R R G(z)w(z)dz G(z)h1 (z)w(z)dz 0 0 e1 (R) = c01 h1 (R) = c h1 (R) > (60) R T R T G(z)h1 (z)dz G(z)h1 (z)dz 0 0 By (53) and (58) (G(z)h1 (z))0 f1 (z) <− (62) G(z)h1 (z) F1 (z) G(z)h1 (z) F1 (z) Inequality (62) implies that R T and R T satisfy the ‘single-crossing’ G(z)h1 (z)dz F1 (z)dz 0 0 condition (the latter crossing ‘from below’) and hence, by (27), ZR G(z)h1 (z) F1 (z) T − T dz > 0 (63) R R 0 G(z)h1 (z)dz F1 (z)dz 0 0 27 for all R, 0 < R < T . In view of (60) and (63), R R R R G(z)h1 (z)w(z)dz F1 (z)w(z)dz 0 0 e1 (R) > c > = c∗ (R) 1 (64) R T R T G(z)h1 (z)dz F1 (z)dz 0 0 ∗ e This inequality and conditions (56) and (11) imply that R1 > R1 . A similar ∗ argument can be used to show that R2 < R e2 . ¥ e Note that it has not been shown whether R1 is 0larger or smaller than 0 e (G(z)h1 (z)) R2 . Indeed, observe that, by (58) and (59), G(z)h1 (z) > (G(z)h22(z)) implying G(z)h (z) G(z)hi (z) that R T , i = 1, 2, satisfy the ‘single-crossing’ condition. Hence, there G(z)hi (z)dz 0 exists an age Rc , 0 < Rc < T , such that G(R)h1 (R) G(R)h2 (R) S , as R S Rc (65) R T R T G(z)h1 (z)dz G(z)h2 (z)dz 0 0 R R G(z)w(z)dz Since ei (R) = c 0 R T hi (R), it follows from (65) that e1 (R) S e2 (R) c c G(z)hi (z)dz 0 e e e e e and φ1 (R) T φ2 (R), as R S Rc . Thus, if R1 < Rc then R1 > R2 , while if e e e R1 > Rc then R1 < R2 . 28 Appendix A Maximization of (40) subject to (42) with respect to c(z), R ≤ z ≤ T , R ˆ and BR yields F.O.C. for the optimum, (ˆ(z), R): c ˆ u0 (ˆR (z)) − v 0 (BR ) = 0, c R≤z≤T (A.1) ˆ ˆ a(RR ) − φR (RR ) = 0 (A.2) where φR (R) = u0 (ˆR (R))w(R), for all R, 0 ≤ R ≤ T . It is seen from (A.1) c that consumption after retirement is constant, cR (z) = cR (R), R ≤ z ≤ T . ˆ ˆ The (Hamiltonian) dynamic optimization condition with respect to c(z), 0 ≤ z ≤ R, is " # c0R (z) ˆ ˆ 1 f (z) v 0 (BR (z)) − u0 (ˆR (z)) c = (A.3) cR (z) ˆ σ F (z) u0 (ˆR (z)) c Note that equation (6) in the paper is a special case of (A.3) when v0 (B) = 0. The two diﬀerential equations (A.3) and (41) in the paper, with initial ˆ condition BR (0) = B0 and the end-condition cR (R) satisfying (A.1) and ˆ ˆ (A.2), determine the optimum path (ˆR (z), BR (z)), 0 ≤ z ≤ R. c The budget constraint, (42) in the paper, and (A.2) are used jointly to ˆ ˆ ˆ solve for RR and cR (RR ). Figure A.1 displays the phase diagram for the optimum path. A higher R corresponds to a higher cR (0). The path drawn ˆ ˆ ˆ R satisfying (A.2), with BR = B0 , i.e. steady state. in the Figure is for R Unlike the model with no bequest motive, optimum consumption ﬁrst increases and then decreases with age. The reason is that the marginal utility of bequests initially exceeds the marginal utility of consumption, leading to accelerated accumulation of assets and slowly increasing consumption. As ˆ assets increase, eventually this relation is reversed. At point A (at age RR ), RR ˆ ˆ ˆ ˆ assets have accumulated to BR (R), where BR (RR ) = (w(z)−ˆR (z))dz+ BR . c ˆ 0 ˆ R RR At this point, cumulative savings ˆ ˆ ˆ (w(z)−ˆR (z))dz > 0 (i.e. BR (RR ) > BR ) e 0 ˆ ˆ ˆ are annuitized to a ﬂow of cR (RR ), reducing assets to BR . 29 ˆ ˆ ˆ The proof that cR (RR ) < c∗ (and hence, by (A.1), BR < B ∗ ), is the same as the proof of Proposition 3 in the paper. The assumption that B0 = BR , i.e.ˆ ˆ ˆ R ) for all z, 0 ≤ z ≤ RR , steady-state, is needed to establish that cR (z) > cR (R ˆ ˆ which is used in that proof. It may not hold for an arbitrary B0 < BR . ˆ 30 Appendix B Groups 2’s survival function, F2 (z), is stochastically dominated by that of group 1, F1 (z). First we want to show that when annuities are priced at the pooled survival function, G(z), and the payment of beneﬁts can be adjusted optimally, group 2 individuals annuitize all their savings. Let e2 (z) be consumption at age z, R ≤ z ≤ T , from non-annuitized resources. The zero-expected proﬁts condition is ZT ZT Z2 R G(z)c(z)dz + G(R) e2 (z)dz − G(z)w(z)dz = 0 (B.1) 0 R2 0 Maximization of expected utility Z2 R ZT Z2 R V2 = F2 (z)u(c2 (z))dz + F2 (z)u(c2 (z) + e2 (z))dz − F2 (z)a(z)dz 0 R2 0 (B.2) subject to (B.1) yields F.O.C. with respect to c(z), R ≤ z ≤ T , F2 (z)u0 (c2 (z) + e(z)) − λ2 G(z) = 0 (B.3) where λ2 , λ2 > 0, is a constant. Hence, for any z, z > R2 , ∂V2 = λ2 [G(z) − G(R2 )] < 0, (B.4) ∂e2 (z) which means that, at the optimum, all savings are annuitized. Suppose now that annuities provide a constant ﬂow of payments, denoted by b. The zero expected proﬁts condition is now ZT ZT Z2 R b2 G(z)dz + G(R2 ) e2 (z)dz − G(z)(w(z) − c2 (z))dz = 0 (B.5) R2 R2 0 31 and expected utility is Z2 R ZT Z2 R V2 = F2 (z)u(c2 (z))dz + F2 (z)u(b2 + e2 (z))dz − F2 (z)a(z)dz = 0 0 R2 0 (B.6) Maximization of V2 subject to (B.5) with respect to e2 (z) and b2 yields F.O.C. F2 (z)u0 (b2 + e2 (z)) − λ2 G(R2 ) = 0, R≤z≤T (B.7) and ZT ZT F2 (z)u0 (b2 + e2 (z))dz − λ2 G(z)dz = 0 (B.8) R2 R2 Suppose that at the optimum, e(z) = 0 for all R2 ≤ z ≤ T . Then, from (B.6) and (B.7), F (R ) ZT ∂V2 2 2 G(R2 ) = λ2 T − T G(z)dz (B.9) ∂e2 |e2 =0 R R F2 (z)dz G(z)dz R2 R2 R2 which, by (53) and (26) in the paper, is positive. Hence, e2 (z) > 0 for some z, R ≤ z ≤ T . Next, we want to show that b2 > 0 at the optimum. Suppose b2 = 0 and hence (B.7) holds for all z, R2 ≤ z ≤ T . Using (B.8), ZT ∂V = λ2 G(R2 )(T − R2 ) − G(z)dz (B.10) ∂b2 |b2 =0 R2 which is positive. Hence, at the optimum b2 > 0. 32 References [1] Abel, A.B. (1986), “Capital Accumulation and Uncertain Lifetimes with Adverse Selection”, Econometrica, 54, 1079-1097. [2] Brugiavini, A. (1993), “Uncertainty Resolution and the Timing of An- nuity Purchases”, Journal of Public Economics, 50, 31-62. [3] Diamond, P. and S. Valdez-Prieto (1994), “Social Security Reforms”, in Bosworth, B., R. Dornbush and R. Labàn (eds.), The Chilean Economy: Policy Lessons and Challenges. (Brookings Institution). [4] Eckstein, Z., M. Eichenbaum and D. Peled (1985), “Uncertain Lifetimes and the Welfare Enhancing Properties of Annuity Markets and Social Security”, Journal of Public Economics, 26, 303-326. [5] Friedman, B.M. and M. Warshawsky (1990), “The Cost of Annuities: Implications for Saving Behavior and Bequest”, Quarterly Journal of Economics, 420, 135-154. [6] Merton, R.C. (1981), “On the Role of Social Security as a Means for Ef- ﬁcient Risk-Bearing in an Economy where Human Capital is not Trade- able”, N.B.E.R. Working Paper, no. 743. [7] Mitchell, O.S., J.R. Poterba, M.J. Warshawsky and J.R. Brown (1999), “New Evidence on Money’s Worth of Individual Annuities”, American Economic Review, (forthcoming). [8] Poterba, J.R. (1997), “The History of Annuities in the United States”, N.B.E.R. Working Paper No. 6001. [9] Rothschild, M. and J. Stiglitz (1976) “Equilibrium in Competitive Insur- ance Markets: an Essay on the Economics of Incomplete Information”, Quarterly Journal of Economics, 90, 624-649 [10] Sheshinski, E. and Y. Weiss (1981), “Uncertainty and Optimal Social Security Systems”, Quarterly Journal of Economics, 95, 189-206. [11] Walliser, J. (1998), “Understanding Adverse Selection in the Annuities Market and the Impact of Privatizing Social Security”, Congressional Budget Oﬃce. 33 [12] Yaari, M.E. (1965), “Uncertain Lifetime, Life Insurance and the Theory of the Consumer”, Review of Economic Studies, 32, 137-150. 34 c ^ cR(Z) ^ cR(R) 0 R T z Figure 1 1 1 = T z2 ∫ F ( z )dz 0 2 F2 ( z ) T ∫ F ( z )dz 0 2 1 1 = T F1 ( z ) z1 ∫ F ( z )dz 1 T 0 ∫ F ( z )dz 0 1 0 zc T z Figure 2 σ >1 φ a( R) ψ (R ) φ R (R) φ (R ) 0 R* ^ RR ^ R T R Figure 3 ψ ( R) = φ R ( R) e φ (R ) 1 0 1 R α Figure 4 ε 1 ε 0 R M θ ∂φ (a) = 1 − σε φ ∂θ 1 σ1 < 1 1− σ1 0 σ >1 R M 1−σ (b) Figure 5 a( R) ψ a’( R) ψ 2 ( R) ψ 1 ( R) 0 ^ ^ R2 R1 1 ^ ^ Rc R` R` 1 R 1 2 α2 α1 Figure 6 u ' (c ) = υ ' ( B )[c ' = 0] ˆ ^ c c* ^ R(0) c c ^ ^ R(RR) 0 ^ B0=BR B* BR ^ R ^ (R ) B Figure A.1