supply demand and uncertainty implications for prelisting conservation policy abstract the endangered species act esa faces a shortage of incentives to motivate the scale of conservation activities necessary to address and reverse the decline of at risk species a recent policy proposal attempts to change this by allowing landowners to generate credits for voluntary prelisting conservation activities we explore the proposed policy from the perspective of potential participants we find that uncertainty present in species listing processes complicates the decision to undertake conservation activities leading to less conservation being supplied than when a listing decision is certain while also delaying implementation until late in the listing determination process incentives created by the prelisting policy may likewise push species status closer to a listing threshold and thus exacerbate uncertainty in the listing process to counter this tendency and encourage a more efficient allocation of conservation activity early actor bonuses weighted credits or limited windows of eligibility could be used to target or place increased premiums on early conservation activity though these findings are most directly applicable to the specific prelisting policy considered here they are nonetheless relevant to a wider array of conservation policies that seek to encourage voluntary early action in advance of a regulatory alternative

credit market constraints consumption smoothing and the accumulation of durable production assets in low income countries investments in bullocks in india in this paper we formulate and estimate a finite horizon structural dynamic model of agricultural investment behavior that incorporates the major features of low income agricultural environments income uncertainty constraints on borrowing and rental markets and the use of investment assets to generate income and smooth consumption the model is fit to longitudinal indian household data on farm profits bullock stocks and pump sets the estimated structural parameters are used to assess the effects on the life cycle accumulation of bullocks agricultural profits and welfare associated with complete markets and bullock liquidity and with second best policies that provide assured sources of income to farmers and weather insurance

discount rates and credit markets theory and evidence from rural india three models of credit markets 1 the permanent income model 2 upward sloping credit supply to individual borrowers and 3 constrained credit due to imperfect enforcement are tested using credit market data and an experimental study of individuals discount rates in south india the permanent income model is rejected by both the discount rate and the credit market data the discount rate data are consistent with either of the other two models while the credit market data are consistent with a combination of these two models other explanations are found to be insufficient to explain the results of this study

the derivation and interpretation of the lucas supply function comment most likely reason for this anomaly is that a large number of the bank failures prior to march 1933 were the result rather than the cause of the rise in the currencydeposit ratio trescott s regressions thereby may increase the degree of feedback raising the measured correlation but biasing upward the estimated effect of bank failures the 1930 panic may have been largely exogenous as noted earlier by wicker but the endogeneity of the subsequent crises has never been seriously questioned if life is to be restored to the view that bank failures were the sole cause of the rise in the currency deposit ratio then those failures must first be shown to be exogenous all that trescott has shown is that one component of the demand for money was highly correlated with bank failures that correlation was never in doubt but it is not sufficient evidence for the conclusions that he draws

testing for liquidity constraints in euler equations with complementary data sources previous tests for liquidity constraints using consumption euler equations have frequently split the sample on the basis of wealth arguing that low wealth consumers are more likely to be constrained we propose alternative tests using different and more direct information on borrowing constraints obtained from the 1983 survey of consumer finances in a first stage we estimate probabilities of being constrained which are then utilized in a second sample the panel study of income dynamics to estimate switching regression models of the euler equation our estimates indicate stronger excess sensitivity associated with the possibility of liquidity constraints than the sample splitting approach

credit as insurance in agrarian economies abstract this paper examines consumption credit as an insurance mechanism in agrarian economies it explains the more rapid adoption of new technology in the green revolution by large farmers who had greater access to consumption credit the paper also demonstrates how the emergence and expansion of consumption credit markets by mitigating the need for hoarding in order to meet consumption contingencies enhances growth by encouraging investment

risk and insurance in a rural credit market an empirical investigation in northern nigeria credit contracts play a direct role in pooling risk between households in northern nigeria repayments owed by borrowers depend on realizations of random shocks by both borrowers and lenders the paper develops two models of state contingent loans the first is a competitive equilibrium in perfectly enforceable contracts the second permits imperfect information and equilibrium default estimates of both models indicate that quantitatively important state contingent payments are embedded in these loan transactions but that a fully efficient risk pooling equilibrium is not achieved the research is based on a year long survey in zaria nigeria conducted by the author

precautionary saving motives an assessment from uk time series of cross sections this paper gauges the strength of precautionary saving motives by estimating the coefficient of prudence from the u k family expenditure survey data set a time series of cross sections the instrumental variables estimates reveal that greater uncertainty systematically leads to larger current savings most of these impacts are large enough to be statistically consistent with widely accepted beliefs about attitudes towards risk so that precautionary saving behavior cannot be refuted moreover the households which are less likely to face liquidity constraints or to share risks are more sensitive to uncertainty finally the households for which the head works in the manufacturing industry are more inclined to self insure against uncertainty copyright 1996 by royal economic society

the economics of conjunctive groundwater management with stochastic surface supplies abstract groundwater management with stochastic surface flows and artificial recharge is considered theoretical analysis characterizes the decision rules and establishes conditions for convergence of socially optimal and common property withdrawals and pumping lifts to limiting probability distributions an empirical application to kern county california finds that optimal withdrawals are generally increasing in hydraulic head and decreasing in surface flows however nonmonotone behavior is observed in some instances artificial recharge is not observed in the limiting distribution due to an interaction of several factors optimal management implies relatively small gains over unregulated groundwater use when preferences are risk neutral

formal and informal risk sharing in ldcs theory and empirical evidence in village economies limited commitment models have been proposed as theoretical alternatives to the complete markets hypothesis and have been shown to be empirically relevant yet village institutions might be able to enforce some contracts we construct a theoretical model which shows how households can insure through both formal and informal contracts when some verifiable production takes place in an environment of incomplete markets this theoretical setting nests the case of complete markets when all risks can be insured by formal contracts because all states of nature would be verifiable and the case where only informal agreements are available agreements specifying informal transfers that needs to be self enforceable we derive two equations of interest the income equation which is partially determined by the formal contract and an euler type equation where consumption growth is affected by lagged consumption instead of being a martingale using semi parametric specifications we derive testable restrictions of our model we estimate both equations using data of village economies in pakistan empirical results are consistent with the model the estimation and allows to show that the incentive constraints due to selfenforcement bind and that formal contracts are used to reduce the probability of binding the constraint

rainwater harvesting and groundwater conservation when endogenous heterogeneity matters in this paper we focus on resource conservation in a model of decentralized management of groundwater and rainwater we show that a conservation policy may have opposite effects on the level of the resource depending on the outcome of the decentralized management more precisely we consider identical farmers who can use two water resources groundwater and or rainwater and we study the symmetric and asymmetric feedback stationary nash equilibria of the dynamic game we show that a subsidy on the use of rainwater may increase the level of the aquifer at the symmetric equilibrium whereas it decreases the level of the aquifer at the asymmetric equilibrium this suggests that the usual focus on interior symmetric equilibria in dynamic games may provide misleading policy implications

precautionary saving under liquidity constraints evidence from rural pakistan this paper investigates precautionary saving under liquidity constraints in pakistan using household panel data in particular while we estimates kimball s 1990 prudence parameter we deviate from dynan s 1993 framework by explicitly considering liquidity constraints as in zeldes 1989 by doing so we attempt to differentiate the standard precautionary saving caused by uncertainty from the one due to liquidity constraints furthermore endogenous liquidity constraints are considered to resolve issues of selection biases in this study we document substantial evidence of the presence of precautionary saving in pakistan more specifically the estimated prudence is significantly higher for liquidity constrained households as compared with unconstrained ones the results support the emerging view that facilitating saving may often be more important than finding better ways of lending to the poor

saving and economic shocks in rural pakistan abstract this paper adapts the recent methodology of paxson to study saving rates in rural pakistan particular attention is paid to differences in marginal rates of financial and physical saving and how these vary across income groups and by direction of income shocks households exhibit more difficulty in smoothing consumption after successive shocks than with a single shock the study also observes marginal rates of saving out of international remittances and lump sum pensions unlike domestic remittances international remittances appear to be treated much as transitory income shocks

the degree of precautionary saving a reexamination abstract extending dynan s methodology dynan k 1993 how prudent are consumers journal of political economy 101 1104 1113 we show that a significant fraction of the prudence parameter puzzle can be explained by a downward omitted variable bias further the estimated prudence is substantially higher for liquidity constrained households

nonmarket institutions for credit and risk sharing in low income countries the design credit and risk institutions in low income countries provides one of the most exciting testing grounds for theories of contracting with imperfect information and limited enforcement this paper reviews some of the recent literature with a special focus on nonmarket institutions that cope with risk and provide credit this literature attempts to bring together insights from economic theory especially information economics contract theory and mechanism design theory however it is also applied being motivated by the circumstance of the poor countries that their authors have visited and studied

who is credit constrained in the u s economy an important assumption of the life cycle model of consumption is the postulate of perfect capital markets this hypothesis has recently been challenged by substantial empirical evidence hall and mishkin 1982 using the panel study of income dynamics estimate that 20 percent of united states families are liquidity constrained mariger 1986 derives a life cycle model with endogenous liquidity constraints and using a cross section estimates this fraction to be 19 4 percent hubbard and judd 1986 simulate a model with a constraint on net worth which shows that with reasonable assumptions about preferences 19 0 percent of united states consumers are liquidity constrained the emerging consensus points therefore to a fraction of approximately 20 percent of the population behaving in a manner that is inconsistent with the pure life cycle model in addition hayashi 1985 and zeldes 1989 investigate the correlation among consumption wealth and income for various population groups and infer that liquidity constraints are more important for younger families with low levels of wealth and saving the main limitation of these studies is that in their data sets constrained consumers are not observable and have to be identified via indirect evidence thus there is as yet little firm evidence about the characteristics of the consumers who are likely to be credit constrained this paper adopts an approach that differs from previous tests for liquidity constraints because it makes use of data where constrained consumers are observable and explicitly links their existence to credit market imperfections and personal characteristics the data drawn from the 1983 survey of consumer finances scf and described in section ii provide information on individuals whose request for credit has been rejected by financial intermediaries in section iii a model is developed in which consumers and lenders behavior jointly determines the probability that a consumer is rationed in the credit market this probability is then

saving and liquidity constraints this paper is concerned with the theory of saving when consumers are not permitted to borrow and with the ability of such a theory to account for some of the stylized facts of saving behavior the models presented in the paper seem to account for important aspects of reality that are not explained by traditional life cycle models copyright 1991 by the econometric society

income smoothing and consumption smoothing one way that risk averse households protect consumption levels is to borrow and use insurance mechanisms another way common in low income economies is to diversify economic activities and make conservative production and employment choices households thus tend toward limiting exposure only to shocks that can be handled with available credit and insurance typically both types of mechanisms are studied independently but much more can be learned by studying them together first we obtain a more complete picture of risks costs and insurance possibilities second it opens the way to considering biases in standard tests of credit and insurance

consumption insurance an evaluation of risk bearing systems in low income economies the hypothesis of full risk sharing can be taken to data from low income countries and evaluate formal and informal financial systems in many contexts idiosyncratic risks are high so credit insurance arrangements could be beneficial statistical tests reveal that households in southern india take advantage of these possibilities villages in cote d ivoire and countries in thailand do not do as well the paper includes an empirical description of the devices used to smooth consumption and a theoretical discussion of private information and incentives on ideal operating systems the full information and mechanism design frameworks provide benchmarks for policy analysis

risk pooling precautionary saving and consumption growth in this paper we model the evolution of income risk and consumption growth we decompose the time series innovation of the income process into its common and cohort specific components from these we compute conditional variances which are used as separate risk terms in a consumption growth equation using a long series of british household data we exploit the time series variation to identify precautionary saving effects and find strong evidence of their importance specifically after allowing for demographic and labour market status there is an independent role for income risk in explaining consumption growth rather than the component that is common across cohorts however it is the cohort specific element that is important in determining changes in consumption growth this result points to a failure of between cohort insurance mechanisms

the effect of liquidity constraints on consumption a cross sectional analysis this paper examines the effect of liquidity constraints on consumption expenditures using a single year cross section data set a reduced form equation for consumption is estimated on high saving households by the tobit procedure to account for the selectivity bias since high saving households are not likely to be liquidity constrained the estimated equation is an appropriate description of how desired consumption that would be forthcoming without liquidity constraints is related to the variables available in the cross section data when the reduced form equation is used to predict desired consumption the gap between desired consumption and measured consumption is most evident for young households

intertemporal substitution and the role of monetary policy new classical macroeconomists have asserted that once one ignores the consequences of sustained expected inflation or what is normally referred to as the tobin effect or inflation tax monetary policy is invariably ineffective both in the long and short run this view is not correct it will be shown that inflation tax free monetary policy rules can have strong stabilisation effects in rational expectations models with intertemporal substitution the best way to eliminate possible inflation tax effects of monetary growth is to assume that as in barro s i976 model the long run expected rate of growth of the money supply is zero more generally if one were concerned exclusively with the effectiveness of stabilisation policy in the new classical sense i e the capability of influencing deviations of actual equilibrium output from its full information level it would be sufficient to postulate that money transfers are simply proportional to pre existing money holdings the a priori exclusion of the tobin effect as a pre requisite for the new classical doctrine is clearly stated in lucas i98i

differential information and the role for active stabilization policy a comment in a recent paper t m anderson analyzes a new classical model in which demanders and suppliers are differentially informed he claims that a particular feedback monetary policy but not a private indexation rule is able to perfectly stablize the economy the authors show that anderson s private indexation rule is also able to perfectly stabilize the economy copyright 1991 by the london school of economics and political science

rational expectations and the role of countercyclical monetary policy the potential role for systematic monetary policy to dampen fluctuations around the natural rate is examined in barro s 1976 model the source of the non neutrality is the effect of nonpermanent changes in the money supply on the inflation rate the real return to money which induces labor leisure substitutions when these non permanent changes take the form of future reactions to imperfectly perceived current disturbances they affect the deviation from the natural rate

informational implications of money interest rate and price rules the information available to private agents determines the effectiveness of various types of monetary policy in an economy in which private agents have differential information sets the ranking of three classes of monetary policy rules critically depends on the specification of agents information sets a price rule for example minimizes the variance of output around its full information level when agents observe both the interest rate and money stock more generally if all three monetary policy variables the money stock the price level and the interest rate are contemporaneously observed the policy ranking is indeterminate

excess sensitivity and asymmetries in consumption an empirical investigation most empirical studies on liquidity constraints classify a consumer as being constrained on the basis of a single indicator such as the asset to income ratio in this analysis the authors model the probability that a consumer faces liquidity constraints as a function of multiple social and economic factors this probability function is estimated simultaneously with the degree of excess sensitivity of consumption to income in a switching regressions framework the switching regressions apply optimal weights to the densities for the euler equations in the two states and are less susceptible to sample misclassification our results based on data from the cex confirm that liquidity constrained consumers are excessively sensitive to variables already known to economic agents however there is also evidence that the unconstrained consumers exhibit behavior that is inconsistent with the theoretical predictions further analysis suggests that such behavior could be explained by time non separable preferences copyright 1997 by ohio state university press

optimal management of a renewable and replaceable resource the case of coastal groundwater the nonrenewable with backstop model of resource management is extended to cover renewables and applied to the case of coastal groundwater in the optimal management trajectory efficiency price exceeds extraction cost by the sum of scarcity rent and drawdown cost the latter remaining large even after the backstop price is reached in the case of rising demand optimal management may call for a stage of conservation followed by a stage of drawdown

current issues in the economics of groundwater resource management the issue of groundwater management remains a practical concern in many regions throughout the world while water managers continue to grapple with the question of how to manage this resource in this article we attempt to bring the most advanced and appropriate tools to bear on the issue of resource allocation involving groundwater our objective is to demonstrate the state of the art in the literature on ways to think about this complex resource and to deal with the important economic issues emanating from its complexity we present the conceptual framework within which economists examine the elements interacting in the management of groundwater resources indicate why the role of the market is limited with respect to the price of this very complex resource and point to the mechanisms that can pull competitive groundwater price and quality graded quantity of groundwater in line with their equilibrium levels in particular we critically review economic models of groundwater use examine the potential for groundwater management discuss the difficulties encountered in the estimation of the relevant control variables of such models and identify the advantages and limitations of the instruments devised for the efficient use allocation of this resource finally we argue that devised regulatory schemes usually ignore the information and knowledge needed for their implementation and we suggest a core of conditions necessary for successful groundwater management reforms

competitive versus efficient extraction of a common property resource the groundwater case abstract in this paper socially optimal and private extraction of a common property aquifer are compared open loop equilibrium and feedback equilibrium in linear strategies have been computed to characterize private extraction the use of these two equilibrium concepts allows us to distinguish between cost and strategic externalities as long as the open loop solution captures only the cost externality and the feedback solution captures both the results show that strategic behaviour increases the overexploitation of the aquifer compared to the open loop solution however if the groundwater storage capacity is large the difference between the socially optimal and private extraction the latter characterized by a feedback equilibrium is negligible

smoothing consumption by smoothing income hours of work responses to idiosyncratic agricultural shocks in rural india while research has demonstrated that farm households in developing economies are able to protect consumption from idiosyncratic crop shocks little evidence shows how this is achieved this paper examines the extent to which labor markets allow households to shift labor from farm to off farm employment and the extent to which such a shift explains the observed lack of correlation between consumption and idiosyncratic crop shocks the empirical analysis uses a novel measure of the idiosyncratic crop income shock which utilizes information on start of season cropping choices to more accurately estimate household expectations of weather

precautionary savings under liquidity constraints a decomposition this paper investigates the effects of liquidity constraints on consumption saving by separating precautionary saving caused by liquidity constraints ps2 from the conventional precautionary saving made against income uncertainty ps1 it is proved that there exists a unique level of wealth below which ps2 is strictly positive and above which liquidity constraints have no effects at all the numerical simulations show that ps2 is quantitatively important depending on age and the level of wealth some empirical findings in the literature cannot be explained by ps1 alone but are consistent with the model in which ps2 is present copyright 1995 by economics department of the university of pennsylvania and the osaka university institute of social and economic research association

savings behaviour in low income countries the empirical literature on savings in low income countries has exploited some remarkable data sets to shed new light on savings behaviour in the poor agricultural households that make up the majority of the population in such countries a number of conclusions have emerged i the degree of consumption smoothing over seasons within the year and across years in response to very large income fluctuations is higher than was supposed ii the lack of complete insurance and credit markets however is manifested in asset stocks and asset compositions among farmers especially small farmers that are inefficient iii the combination of low and volatile incomes is an important cause of inefficiency and income inequality iv the proximity of formal financial institutions increases financial savings and crowds out informal insurance arrangements thus in principle better facilitating financial intermediation and iv simple life cycle models of savings do not appear to explain long term savings in low income settings copyright 2001 oxford university press

joint quantity quality management of groundwater economic literature on groundwater managementhas traditionally been split into two areas there are papers that evaluate different schemes of dynamicaquifer management considering that pumping costs vary with stock but ignoring water quality on the other hand there are papers that considercontamination problems caused by specificpollutants this paper presents two alternative models for joint quantity quality management and it shows that existing models are in fact special cases of these the framework isdynamic and considers both the stock of waterquantity and a stock measure of water quality optimal taxes are derived and shown to be different from those in existing quantity only or quality only models implementationproblems are briefly discussed

intertemporal substitution and the role of monetary policy policy irrelevance once again recently marini i985 demonstrates that feedback policy is effective in barro s i976 model even in the absence of differentially informed agents or non proportional money transfers in particular marini demonstrates that a policy rule with feedback to the current money stock from disturbances dated t 2 or further in the past will be effective at fully stabilising output in barro s model this paper demonstrates that this policy effectiveness result is dependent on an implicit assumption that the length of private agents horizon falls short of the length of the lags in the feedback rule more generally this paper points out that a crucial feature of barro s i976 model is the specification of the decision horizon of private agents relative to the lag on demand disturbances in the monetary rule if the feedback lag in the monetary rule exceeds the horizons of private agents then monetary policy can stabilise output if the horizon of private agents is equal to or exceeds the lags in the monetary rule

strategic behavior and efficiency in the common property extraction of groundwater groundwater has always been regarded as a common property resource where entry is restricted by land ownership and private exploitation is inefficient in 1980 gisser and sanchez presented a first estimation of this inefficiency cornparing socially optimal exploitation with private competitive exploitation using a model with linear water demand average extraction cost independent of the rate of extraction and linearly decreasing with respect to the water table level they characterized the private exploitation of the aquifer assuming that farmers are myopic and choose their rate of extraction to maximize their current profits whereas optimal exploitation is obtained by maximizing the present value of the stream of aggregate profits their results show that if the storage capacity of the aquifer is relatively large the difference between the two systems is so small that it can be ignored for practical consideration this result has been called the gisser sanchez rule by nieswiadomy 1985 and it has and important policy implication regulation of the resource does not seem justified since the profits it brings are not very high 1

decreasing relative risk aversion and tests of risk sharing the relative risk aversion rra coefficient of a household whose consumption is close to the subsistence level may be very high for example if consumption is exactly at the subsistence level the household may not be willing to bear any risk if this is the case then the rra coefficient must be a decreasing function of wealth for poor households therefore we should allow the possibility of decreasing rra drra in testing the full risk sharing hypothesis however existing tests in the empirical literature are derived using preferences that exhibit either increasing or constant rra even when they are applied to data containing low income households we therefore use a hyperbolic absolute risk aversion hara utility which implies increasing constant and decreasing rra as special cases to test full risk sharing hypothesis using the international food policy research institute ifpri and the international crops research institute of the semi arid tropics icrisat household level data sets we find evidence in support of the drra hypothesis along with evidence favoring full risk sharing hypothesis at the village level and evidence against the hypothesis at the inter village level when rra is restricted to be constant we replicate the previous results in the literature reject the full risk sharing hypothesis at both levels our tests however reject this restriction and favor drra in almost all cases these results suggest that it is important to allow for drra in testing the full risk sharing hypothesis when data containing low income households are investigated this abstract was borrowed from another version of this item this abstract was borrowed from another version of this item this abstract was borrowed from another version of this item this abstract was borrowed from another version of this item this abstract was borrowed from another version of this this abstract was borrowed from another version of this item

risk and household grain management in developing countries a dynamic model is presented of a household s joint production storage and trade decisions when facing transaction costs and risk in prices and yields grain management decisions balance the goals of maximising profits and reducing consumption price risk model solutions calibrated to chinese data show that grain s consumption role makes it an attractive form of precautionary saving even when households have access to credit the joint nature of production and savings decisions limits the income loss associated with risk coping and the desire to store grain can explain why subsistence households are frequently net purchasers but rarely net sellers of grain

how prudent are consumers using data from the consumer expenditure survey this paper presents a simple test that provides an explicit estimate of the parameter in the utility function that reflects the strength of the precautionary saving motive the coefficient of relative prudence the test yields a fairly precise estimate of a small precautionary motive in fact the estimate is too small to be consistent with widely accepted beliefs about risk aversion the presence of liquidity constrained households does not appear to explain this finding and there is some evidence that self selection of households into risky environments also cannot explain the results

unemployment and liquidity constraints summary we present a dynamic framework for the interaction between borrowing liquidity constraints and deviations of actual hours from desired hours both measured by discrete valued indicators and estimate it as a system of dynamic binary and ordered probit models with panel data from the panel study of income dynamics we analyze a household s propensity to be liquidity constrained by means of a dynamic binary probit model we analyze qualitative aspects of the conditions of employment namely whether the household head is involuntarily overemployed voluntarily employed or involuntarily underemployed or unemployed by means of a dynamic ordered probit model we focus on the possible interaction between the two types of constraints we estimate these models jointly using maximum simulated likelihood where we allow for individual random effects along with an autoregressive process for the general error term in each equation a novel feature of our method is that it allows for the random effects to be correlated with regressors in a time invariant fashion our results provide strong support for the basic theory of constrained behavior and the interaction between liquidity constraints and exogenous constraints on labor supply copyright 2007 john wiley sons ltd

an exogeneity test for a simultaneous equation tobit model with an application to labor supply a test of weak exogeneity in the simultaneous equation tobit model is proposed and illustrated using a female labour supply model estimated using cross section data the test statistic can be simply output from any standard tobit maximum likelihood package and is asymptotically efficient the procedure provides consistent estimators for the simultaneous tobit model whose asymptotic covariance matrix is a simple extension of the usual tobit formula we also provide the lagrange multiplier test of weak exogeneity this abstract was borrowed from another version of this item

precautionary saving in the small and in the large the theory of precautionary saving is shown to be isomorphic to the arrow pratt theory of risk aversion making possible the application of a large body of knowledge about risk aversion to precautionary saving and more generally to the theory of optimal choice under risk in particular a measure of the strength of the precautionary saving motive analogous to the arrow pratt measure of risk aversion is used to establish a number of new propositions about precautionary saving and to give a new interpretation of the dreze modigliani substitution effect copyright 1990 by the econometric society

on the concavity of the consumption function at least since keynes 1935 many economists have had the intuition that the marginal propensity to consume out of wealth declines as wealth increases nonetheless standard perfect certainty and certainty equivalent versions of intertemporal optimizing models of consumption imply a marginal propensity to consume that is unrelated to the level of household wealth we show that adding income uncertainty to the standard optimization problem induces a concave consumption function in which as keynes suggested the marginal propensity to consume out of wealth or transitory income declines with the level of wealth