Complexity and Bounded Rationality in Individual Decision Problems

I develop a model of endogenous bounded rationality due to search costs, arising implicitly from the decision problem's complexity. The decision maker is not required to know the entire structure of the problem when making choices. She can think ahead, through costly search, to reveal more of its details. However, the costs of search are not assumed exogenously; they are inferred from revealed preferences through choices. Thus, bounded rationality and its extent emerge endogenously: as problems become simpler or as the benefits of deeper search become larger relative to its costs, the choices more closely resemble those of a rational agent. For a fixed decision problem, the costs of search will vary across agents. For a given decision maker, they will vary across problems. The model explains, therefore, why the disparity, between observed choices and those prescribed under rationality, varies across agents and problems. It also suggests, under reasonable assumptions, an identifying prediction: a relation between the benefits of deeper search and the depth of the search. In decision problems with structure that allows the optimal foresight of search to be revealed from choices of plans of action, the relation can be tested on any agent-problem pair, rendering the model falsifiable. Moreover, the relation can be estimated allowing the model to make predictions with respect to how, in a given problem, changes in the terminal payoffs affect the depth of search and, consequently, choices. My approach provides a common framework for depicting the underlying limitations that force departures from rationality in different and unrelated decision-making situations. I show that it is consistent with violations of timing-independence in temporal framing problems, dynamic inconsistency and diversification bias in sequential versus simultaneous choice problems, and with plausible but contrasting risk attitudes across small- and large-stakes gambles.bounded rationality, complexity, search

Efficient Nash Equilibrium under Adverse Selection

This paper revisits the problem of adverse selection in the insurance market of Rothschild and Stiglitz (1976). We propose a simple extension of the game-theoretic structure in Hellwig (1987) under which Nash-type strategic interaction between the informed customers and the uninformed firms results always in a particular separating equilibrium. The equilibrium allocation is unique and Pareto-efficient in the interim sense subject to incentive-compatibility and individual rationality. In fact, it is the unique neutral optimum in the sense of Myerson (1983).Insurance Market; Adverse Selection; Incentive Efficiency

Other Assets' Risk: Asset-Prices and Perceptions of Asset-Risk

Due to wealth effects, the price of a security may vary with the realization of an underlying risk factor even when the security's dividend is independent of that factor. This paper highlights a crucial component of these effects hitherto ignored by the literature: changes in wealth do not alter only an agent's risk aversion, but also her perceived "riskiness" of the security. The latter enhances significantly the extent to which market-clearing leads to endogenously-generated correlation across asset prices and returns, over and above that induced by correlation between payoffs, giving the appearance of "contagion".General Equilibrium Asset-Pricing; Lucas Trees; Contagion

Preference Conditions for Linear Demand Functions

The present study takes consumer preferences as the primitive and a most general formulation of a linear demand system as the desideratum. To investigate how the two are related, I take a novel approach to demand integrability that relies on some recent results in Diasakos and Gerasimou (2020). The methodology applies for either of the two possible price-normalization regimes (with respect to the price of a numeraire commodity or income); in either case, it leads to a complete characterization of linear demand systems in terms of the properties for the underlying rationalizing preference relation, and analytical solutions for the corresponding (direct) utility function. My results provide a proper microfoundation for linear demand systems-in a way that addresses knowledge gaps in the extant literature on linear demand that leave space for fundamental misunderstanding. JEL Classifications: C02, D01, D11 An earlier version was presented at a session of the 20th annual SAET conference; I wish to thank the participants for helpful comments

Comparative Statics of Asset Prices: the effect of other assets' risk

Currently, financial economics is unable to predict changes in asset prices with respect to changes in the underlying risk factors, even when an asset's dividend is independent of a given factor. This paper takes steps towards addressing this issue by highlighting a crucial component of wealth effects on asset prices hitherto ignored by the literature. Changes in wealth do not only alter an agents risk aversion, but also her perceived 'riskiness' of a security. The latter enhances significantly the extent to which market- clearing leads to endogenously-generated correlation across asset prices, over and above that induced by correlation between payoffs, giving the appearance of 'contagion.

Preference Conditions for Linear Demand Functions

The present study takes consumer preferences as the primitive and a most general formulation of a linear demand system as the desideratum. To investigate how the two are related, I take a novel approach to demand integrability that relies on some recent results in Diasakos and Gerasimou (2020). The methodology applies for either of the two possible price-normalization regimes (with respect to the price of a numeraire commodity or income); in either case, it leads to a complete characterization of linear demand systems in terms of the properties for the underlying rationalizing preference relation, and analytical solutions for the corresponding (direct) utility function. My results provide a proper microfoundation for linear demand systems-in a way that addresses knowledge gaps in the extant literature on linear demand that leave space for fundamental misunderstanding. JEL Classifications: C02, D01, D11 An earlier version was presented at a session of the 20th annual SAET conference; I wish to thank the participants for helpful comments

Preference Conditions for Invertible Demand Functions

It is frequently assumed in several domains of economics that demand functions are invertible in prices. At the primitive level of preferences, however, the corresponding characterization has remained elusive. We identify necessary and sufficient conditions on a utility-maximizing consumer's preferences for her demand function to be continuous and invertible: strict convexity, strict monotonicity and differentiability in the sense of Rubinstein (2006). We further show that Rubinstein differentiability is equivalent to the indifference sets being smooth, which is weaker than Debreu's (1972) notion of preference smoothness. We finally discuss implications of our analysis for demand functions that satisfy the "strict law of demand"

Preference Conditions for Invertible Demand Functions

It is frequently assumed in several domains of economics that demand functions are invertible in prices. At the primitive level of preferences, however, the corresponding characterization has remained elusive. We identify necessary and sufficient conditions on a utility-maximizing consumer's preferences for her demand function to be continuous and invertible: strict convexity, strict monotonicity and differentiability in the sense of Rubinstein (2006). We further show that Rubinstein differentiability is equivalent to the indifference sets being smooth, which is weaker than Debreu's (1972) notion of preference smoothness. We finally discuss implications of our analysis for demand functions that satisfy the "strict law of demand"

Preference Conditions for Invertible Demand Functions

It is frequently assumed in several domains of economics that demand functions are invertible in prices. At the primitive level of preferences, however, the corresponding characterization has remained elusive. We identify necessary and sufficient conditions on a utility-maximizing consumer's preferences for her demand function to be continuous and invertible: strict convexity, strict mono-tonicity and differentiability in the sense of Rubinstein (2006). We further show that Rubinstein differ-entiability is equivalent to the indifference sets being smooth, which is weaker than Debreu's (1972) notion of preference smoothness. We finally discuss implications of our analysis for demand functions that satisfy the "strict law of demand". * We are grateful to Hugo Sonnenschein, Phil Reny and the anonymous referees for very useful comments. Any errors are our own

Rationalizable Suicides: Evidence from Changes in Inmates’ Expected Length of Sentence

Is there a rational component in the decision to commit suicide? Economists have been trying to shed light on this question by studying whether suicide rates are related to contemporaneous socioeconomic conditions. This paper goes one step further: we test whether suicides are linked to forward-looking behavior. In Italy, collective sentence reductions (pardons) often lead to massive releases of prisoners. More importantly, they are usually preceded by prolonged parliamentary activity (legislative proposals, discussion, voting, etc.) that inmates seem to follow closely. We use the legislative proposals for collective pardons to measure changes in the inmates’ expectations about the length of their sentences, and find that suicide rates tend to be significantly lower when pardons are proposed in congress. This suggests that, among inmates in Italian prisons, the average decision to commit suicide responds to changes in current expectations about future conditions. At least partially, therefore, the decision seems rationalizable