Repeated Games with Present-Biased Preferences

We study infinitely repeated games with observable actions, where players have present-biased (so-called beta-delta) preferences. We give a two-step procedure to characterize Strotz-Pollak equilibrium payoffs: compute the continuation payoff set using recursive techniques, and then use this set to characterize the equilibrium payoff set U(beta,delta). While Strotz-Pollak equilibrium and subgame perfection differ here, the generated paths and payoffs nonetheless coincide. We then explore the cost of the present-time bias. Fixing the total present value of 1 util flow, lower beta or higher delta shrinks the payoff set. Surprisingly, unless the minimax outcome is a Nash equilibrium of the stage game, the equilibrium payoff set U(beta,delta) is not separately monotonic in beta or delta. While U(beta,delta) is contained in payoff set of a standard repeated game with smaller discount factor, the present-time bias precludes any lower bound on U(beta,delta) that would easily generalize the beta=1 folk-theorem.beta-delta preferences, repeated games, dynamic programming, Strotz-Pollak equilibrium

The College Admissions Problem Under Uncertainty

We consider a college admissions problem with uncertainty. We realistically assume that (i) students' college application choices are nontrivial because applications are costly, (ii) college rankings of students are noisy and thus uncertain at the time of application, and (iii) matching between colleges and students takes place in a decentralized setting. We analyze a general equilibrium model where two ranked colleges set admissions standards for student quality signals, and students, knowing their types, decide where to apply to. We show that the optimal student application portfolio need not be monotone in types, and we construct a robust example to show that this can lead to a failure of assortative matching in equilibrium. More importantly, we prove that a unique equilibrium with assortive matching exists provided application costs are small and the lower-ranked college has sufficiently high capacity. We also provide equilibrium comparative static results with respect to college capacities and application costs. We apply the model to the question of race-based admissions policiesmatching, directed search, noise

Simultaneous Search

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75607/1/j.1468-0262.2006.00705.x.pd

Increasing Returns in the Value of Information

Is there an intrinsic nonconcavity to the value of information? In an influential paper, Radner and Stiglitz (1984, henceforth RS) suggests that there is. They demonstrated, in a seemingly general model, that the marginal value of a small amount of information is zero. Since costless information is always (weakly) valuable, this finding implies that, unless the information is useless, it must exhibit increasing marginal returns over some range. RS do present a few examples that violate their assumptions for which information exhibits decreasing marginal returns. Yet, the conditions under which they obtain the nonconcavity do not seem initially to be overly strong. They index the information structure, represented by a Markov matrix of state-conditional signal distributions, by a parameter representing the `amount' of information, with a zero level of the parameter representing null information. The main assumption is that this Markov matrix be a differentiable in the index parameter at null information, which seems to be a standard smoothness assumption. As noted by RS, this nonconcavity has several implications: the demand for information will be a discontinuous function of its price; agents will not buy `small' quantities of information; and agents will tend to specialize in information production. The nonconcavity has been especially vexing to the literature on experimentation. If the value of information is not concave in the present action, then the analysis of optimal experimentation is much more complex. Moreover, some recent papers have considered experimentation in strategic settings (Harrington (JET 1995); Mirman, Samuelson and Schlee (JET 1994)). In these models, the nonconcavity means that the best reply mappings may not be convex-valued, so that pure strategy equilibria may not exist. The purpose of this paper is to re-examine the conditions under which a small amount of information has zero marginal value. Much of the experimentation and information demand literature has assumed either an infinite number of signal realizations or an infinite number of states, unlike the finite RS framework. Our objective is to clarify the conditions under which the nonconcavity holds in this more common framework. This general setting will help us to evaluate the robustness of the nonconcavity. We find that the assumptions required to obtain the nonconcavityare fairly strong; although some of the assumptions are purely technical, most are substantive: we present examples showing that their failure leads to a failure of nonconcavity.

A Supply and Demand Model of the College Admissions Problem

We develop the first Bayesian model of decentralized college admissions, with heterogeneous students, costly portfolio applications, and noisy college evaluations. Students face a nontrivial portfolio choice, and colleges choose admissions standards that act like market-clearing prices. We derive the two college model equilibrium, deriving a “law of demand”. Surprisingly, the worse college might impose higher standards, and weaker students sometimes apply more aggressively. The lesser college impacts its rival through student portfolio reallocation. Also, the weaker college counters affirmative action at its rival with a discriminatory admissions policy, and may poach students from its rival using early admissions.Economic

Repeated Games with Present-Biased Preferences

We study infinitely repeated games with observable actions, where players have present-biased (so-called beta-delta) preferences. We give a two-step procedure to characterize Strotz–Pollak equilibrium payoffs: compute the continuation payoff set using recursive techniques, and then use this set to characterize the equilibrium payoff set U(beta,delta). While Strotz–Pollak equilibrium and subgame perfection differ here, the generated paths and payoffs nonetheless coincide. We then explore the cost of the present-time bias. Fixing the total present value of 1 util flow, lower beta or higher delta shrinks the payoff set. Surprisingly, unless the minimax outcome is a Nash equilibrium of the stage game, the equilibrium payoff set U(beta,delta) is not separately monotonic in beta or delta. While U(beta,delta) is contained in payoff set of a standard repeated game with smaller discount factor, the present-time bias precludes any lower bound on U(beta,delta) that would easily generalize the beta = 1 folk-theorem