Commitment and self-control

The literature on self-control problems has typically concentrated on immediate temptations. This paper studies a Gul and Pesendorfer [Temptation and self-control, Econometrica 69 (2001) 1403-1435; Self-control and the theory of consumption, Econometrica 72 (2004) 119-158] style model in which decision-makers are affected by temptations that lie in the future. While temptation is commonly understood to give rise to a demand for commitment, it is shown that ‘temptation by future consumption’ can induce its absence. The model also exhibits procrastination, provides an alternative to projection bias as an explanation for some experimental results, and can simultaneously account for myopic and hyperopic behavior. The evidence on preference reversals supports temptation by future consumption, and suggests that it may not be restricted to short time horizons.     

Probabilistic representation of complexity

We introduce a framework to study individuals’ behavior in environments that are deterministic, but too complex to permit tractable deterministic representations. An agent in these environments uses a probabilistic model to cope with his inability to think through all contingencies in advance. We interpret this probabilistic model as embodying all patterns the agent perceives, yet allowing for the possibility that there may be important details he had missed. Although the implied behavior is rational, it is consistent with an agent who believes his environment is too complex to warrant precise planning, foregoes finely detailed contingent rules in favor of vaguer plans, and expresses a preference for flexibility.     

Consumption dynamics in general equilibrium: A characterisation when markets are incomplete

We introduce a methodology for analysing infinite horizon economies with two agents, one good, and incomplete markets. We provide an example in which an agent's equilibrium consumption is zero eventually with probability one even if she has correct beliefs and is marginally more patient. We then prove the following general result: if markets are effectively incomplete forever then on any equilibrium path on which some agent's consumption is bounded away from zero eventually, the other agent's consumption is zero eventually—so either some agent vanishes, in that she consumes zero eventually, or the consumption of both agents is arbitrarily close to zero infinitely often. Later we show that (a) for most economies in which individual endowments are finite state time homogeneous Markov processes, the consumption of an agent who has a uniformly positive endowment cannot converge to zero and (b) the possibility that an agent vanishes is a robust outcome since for a wide class of economies with incomplete markets, there are equilibria in which an agent's consumption is zero eventually with probability one even though she has correct beliefs as in the example. In sharp contrast to the results in the case studied by Sandroni (2000) [29] and Blume and Easley (2006) [8] where markets are complete, our results show that when markets are incomplete not only can the more patient agent (or the one with more accurate beliefs) be eliminated but there are situations in which neither agent is eliminated.     

Consumption choice and asset pricing with a non-price-taking agent

Summary. This paper develops a pure-exchange model to study the consumption-portfolio problem of an agent who acts as a non-price-taker, and to analyze the implications of his behavior on equilibrium security prices. The non-price-taker is modeled as a price leader in all markets; his price impact is then recast as a dependence of the Arrow-Debreu prices on his consumption, allowing a tractable formulation. Besides the aggregate consumption, the endowment of the non-price-taker appears as an additional factor in driving equilibrium allocations and prices. Comparisons of equilibria between a price-taking and a non-price-taking economy are carried out. Received: March 29, 1996; revised version October 29, 1996     

Optimal contracting with dynastic altruism: Family size and per capita consumption

We use a Barro–Becker model of endogenous fertility, in which parents are subject to idiosyncratic shocks that are private information (either to labor productivity or taste for leisure), to study the efficient degree of consumption inequality in the long run. The planner uses the trade-off between family size and future consumption and leisure, to provide incentives for workers to reveal their shocks. We show that in this environment, the optimal dynamic contract no longer features immiseration in consumption. We also discuss the implications of the model on the long run properties of family size in the optimal contract and show that the long run trend in dynasty size can be either positive or negative depending on parameters.     

Modeling internal commitment mechanisms and self-control: A neuroeconomics approach to consumption–saving decisions

We provide a new model of consumption–saving decisions which explicitly allows for internal commitment mechanisms and self-control. Agents have the ability to invoke either automatic processes that are susceptible to the temptation of ‘over-consuming,’ or alternative control processes which require internal commitment but are immune to such temptations. Standard models in behavioral economics ignore such internal commitment mechanisms. We justify our model by showing that much of its construction is consistent with dynamic choice and cognitive control as they are understood in cognitive neuroscience.The dynamic consumption–saving behavior of an agent in the model is characterized by a simple consumption–saving goal and a cut-off rule for invoking control processes to inhibit automatic processes and implement the goal. We discuss empirical tests of our model with available individual consumption data and we suggest critical tests with brain-imaging and experimental data.     

The micro economics of group behavior: General characterization

We study the demand function of a group of S members facing a global budget constraint. Any vector belonging to the budget set can be consumed within the group, with no restriction on the form of individual preferences, the nature of individual consumptions or the form of the decision process beyond efficiency. Moreover, only the group aggregate behavior, summarized by its demand function, is observable. We provide necessary and (locally) sufficient restrictions that fully characterize the group's demand function, with and without distribution factors. We show that the private or public nature of consumption within the group is not testable from aggregate data on group behavior.     

An Afriat Theorem for the collective model of household consumption

We provide a nonparametric ‘revealed preference’ characterization of rational household behavior in terms of the collective consumption model, while accounting for general individual preferences that can be non-convex. Our main result is the Collective Afriat Theorem, which parallels the well-known Afriat Theorem for the unitary model. First, it provides a characterization of collectively rational consumption behavior in terms of collective Afriat inequalities. Next, it implies the Collective Axiom of Revealed Preference (CARP) as a testable necessary and sufficient condition for data consistency with collective rationality. Finally, the theorem has some interesting testability implications. With only a finite set of observations, the nature of consumption externalities (positive or negative) in the intra-household allocation process is non-testable. The same non-testability conclusion holds for privateness (with or without externalities) or publicness of consumption. By contrast, concavity of individual utility functions (representing convex preferences) turns out to be testable. In addition, monotonicity is testable for the model that assumes all household consumption is public.     

Optimal risk sharing and borrowing constraints in a continuous-time model with limited commitment

We study a continuous-time version of the optimal risk-sharing problem with one-sided commitment. In the optimal contract, the agent?s consumption is a time-invariant, strictly increasing function of a single state variable: the maximal level of the agent?s income realized to date. We characterize this function in terms of the agent?s outside option value function and the discounted amount of time in which the agent?s income process is expected to reach a new to-date maximum. Under constant relative risk aversion we solve the model in closed-form: optimal consumption of the agent equals a constant fraction of his maximal income realized to date. In the complete-markets implementation of the optimal contract, the Alvarez–Jermann solvency constraints take the form of a simple borrowing constraint familiar from the Bewley–Aiyagari incomplete-markets models.     

The role of low expectations in health and education investment and hazardous consumption

Abstract .  Young people with little 'social or health capital' may be more likely to take up hazardous consumption and shun investments in human capital, raising their likelihood of a 'rags to rags' sequence. First, diminishing marginal utility could raise the marginal benefit of hazardous consumption and the cost of investment. But poor youths may also have lower expectations of future success, independent of the choices they make. Lower expectations of success could reduce the future cost of hazardous consumption and benefit of investment. We test the effect of expectations on decisions to smoke, drink hazardously, exercise, and complete high school, using a longitudinal study of youth in New Zealand. We find that 15-year-olds' expectations of success predict the subsequent onset of smoking, lack of exercise, and failure to complete high school, but not hazardous drinking. While some of the influence of expectations can be explained by low social and health capital, IQ, and other factors, expectations retain a direct effect on smoking and exercise once these other factors are controlled for.     

Optimal use of correlated information in mechanism design when full surplus extraction may be impossible

We study the mechanism design problem when the principal can condition the agent's transfers on the realization of ex post signals that are correlated with the agent's types. Crémer and McLean [Econometrica 53(1985) 345-361; 56(1988) 1247-1257], McAfee and Reny [Econometrica 60(2)(1992) 395-421], and Riordan and Sappington [J. Econ. Theory, 45(1988) 189-199] studied situations where the signals are such that full surplus can be extracted from every agent type. We study optimal utilization of the signals when there are fewer signals than types and the Riordan and Sappington conditions do not always hold. For some special cases, we show the level of surplus that can be extracted, and identify the agent types who obtain rent.     

Optimal growth and uncertainty: Learning

We introduce learning in a Brock-Mirman environment and study the effect of risk generated by the planner's econometric activity on optimal consumption and investment. Here, learning introduces two sources of risk about future payoffs: structural uncertainty and uncertainty due to the anticipation of learning. The latter renders control and learning nonseparable. We present two sets of results in a learning environment. First, conditions under which the introduction of learning increases or decreases optimal consumption are provided. The effect depends on the strengths and directions of the two sources of risk, which may pull in opposite directions. Second, the effects of the mean and riskiness of the distribution of the signal and initial beliefs on optimal consumption are studied.     

Theories of behavior in principal-agent relationships with hidden action

In a laboratory experiment, we investigate behavior in a principal-agent situation with moral hazard. We evaluate the predictive success of two theories. One is the standard agency theory, which assumes that the agent will accept any contract offer that satisfies his participation constraint, typically requiring zero expected utility. The other is the “fair-offer” theory suggested by Keser and Willinger [2000. Principals’ principles when agents’ actions are hidden. International Journal of Industrial Organization 18 (1), 163-185], which requires that the principal provide full insurance against losses to the agent and leave him a share of at most 50% of the generated surplus. The treatment variable of our experiment is the cost of effort. As effort costs increase, expected net surplus of a contract decreases. We observe that fair-offer theory generally predicts observed contract offers better than standard agency theory. However, the predictive success of the fair-offer theory decreases, while the one of standard agency theory increases with decreasing expected net surplus.     

Task assignment under agent loss aversion

We analyze a task-assignment model in which a principal assigns a task to one of two agents depending on future states. If the agents have concave utility, the principal assigns the task to them contingent on the state. We show that if the agents are loss averse, a state-independent assignment–assigning the task to a single agent in all states–can be optimal even when the principal can write a contingent contract at no cost.     

Endogenous supply of fiat money

We consider whether reputation concerns can discipline the behavior of a long-lived self-interested agent who has a monopoly over the provision of fiat money. We obtain that when this agent can commit to a choice of money supply, there is a monetary equilibrium where it never overissues. We show, however, that monetary equilibria with no overissue do not exist when there is no commitment. This happens because the incentives this agent has to maintain a reputation for providing valuable currency disappear once its reputation is high enough. More generally, we prove that in the absence of commitment overissue happens infinitely often in any monetary equilibrium. We conclude by showing that imperfect memory can restore the positive result obtained with commitment.     

Subjective random discounting and intertemporal choice

This paper provides an axiomatic foundation for a particular type of preference shock model called the random discounting representation where a decision maker believes that her discount factors change randomly over time. For this purpose, we formulate an infinite horizon extension of [E. Dekel, B. Lipman, A. Rustichini, Representing preferences with a unique subjective state space, Econometrica 69 (2001) 891-934], and identify the behavior that reduces all subjective uncertainties to those about future discount factors. We also show uniqueness of subjective belief about discount factors. Moreover, a behavioral comparison about preference for flexibility characterizes the condition that one's subjective belief second-order stochastically dominates the other. Finally, the resulting model is applied to a consumption-savings problem.     

Growth with many agents and wages paid ex ante

In this paper, we consider a one-sector model of economic growth with several infinitely-lived heterogeneous agents, who are endowed with diverse discount factors as well as preferences over consumption. In line with the classical Ramsey model, agents are not allowed to borrow against future income. Unlike the traditional assumption of ex post wage payment, wages are paid ex ante in our model. We first explain the difference between the assumptions of wages being paid ex ante and wages being paid ex post in the framework of a simple illustrative two-class model. Our main result shows that in contrast to the many-agent Ramsey model with ex post wage payment, the capital stock sequence converges to the steady state stock irrespective of production technology employed by the firms. Further, all impatient agents own zero capital stock, whereas the most patient agent owns the entire capital stock from some time onward. Thus, we have shown that a slight modification in the timing of wage payment in growth models can lead to significant changes in the stability properties of equilibrium dynamics.     

On Ramsey's conjecture: efficient allocations in the neoclassical growth model with private information

In his seminal paper of 1928, Ramsey conjectured that if agents discounted the future differently, in the long run all agents except the most patient would live at the subsistence level. The validity of this conjecture was investigated in different environments. In particular, it has been confirmed in the neoclassical growth model with dynamically complete markets. This paper studies this conjecture in a version of this model that includes private information and heterogeneous agents. A version of Bayesian implementation is introduced and a recursive formulation of the original allocation problem is established. Efficient allocations are renegotiation-proof and the expected utility of any agent cannot go to zero with positive probability if the economy does not collapse. If the economy collapses all agents will get zero consumption forever. Thus, including any degree of private information in the neoclassical growth model will deny Ramsey's conjecture, if efficient allocations are considered.     

Internal rationality, imperfect market knowledge and asset prices

We present a decision theoretic framework in which agents are learning about market behavior and that provides microfoundations for models of adaptive learning. Agents are ‘internally rational’, i.e., maximize discounted expected utility under uncertainty given dynamically consistent subjective beliefs about the future, but agents may not be ‘externally rational’, i.e., may not know the true stochastic process for payoff relevant variables beyond their control. This includes future market outcomes and fundamentals. We apply this approach to a simple asset pricing model and show that the equilibrium stock price is then determined by investors? expectations of the price and dividend in the next period, rather than by expectations of the discounted sum of dividends. As a result, learning about price behavior affects market outcomes, while learning about the discounted sum of dividends is irrelevant for equilibrium prices. Stock prices equal the discounted sum of dividends only after making very strong assumptions about agents? market knowledge.     

Strategic Ignorance as a Self-Disciplining Device

We analyse the decision of an agent with time-inconsistent preferences to consume a good that exerts an externality on future welfare. The extent of the externality is initially unknown, but may be learned via a costless sampling procedure. We show that when the agent cannot commit to future consumption and learning decisions, incomplete learning may occur on a Markov perfect equilibrium path of the resulting intra-personal game. In such a case, each agent's incarnation stops learning for some values of the posterior distribution of beliefs and acts under self-restricted information. This conduct is interpreted as strategic ignorance. All equilibria featuring this property strictly Pareto dominate the complete learning equilibrium for any posterior distribution of beliefs.