Bruno Strulovici

COMPARATIVE STATICS, INFORMATIVENESS, AND THE INTERVAL DOMINANCE ORDER

We identify a new way to order functions, called the interval dominance order, that generalizes both the single crossing property and a standard condition used in statistical decision theory. This allows us to provide a unified treatment of the major theorems on monotone comparative statics with and without uncertainty, the comparison of signal informativeness, and a non-Bayesian theorem on the completeness of increasing decision rules. We illustrate the concept and results with various applications, including an application to optimal stopping time problems where the single crossing property is typically violated. Copyright 2009 The Econometric Society.

Aggregating the Single Crossing Property

The single crossing property plays a crucial role in economic theory, yet there are important instances where the property cannot be directly assumed or easily derived. Difficulties often arise because the property cannot be aggregated: the sum or convex combination of two functions with the single crossing property need not have that property. We introduce a new condition characterizing when the single crossing property is stable under aggregation, and also identify sufficient conditions for the preservation of the single crossing property under multidimensional aggregation. We use our results to establish properties of objective functions (convexity, logsupermodularity), the monotonicity of optimal decisions under uncertainty, and the existence of monotone equilibria in Bayesian games.

Increasing interdependence of multivariate distributions

Orderings of interdependence are useful in many economic contexts: in assessing ex post inequality under uncertainty; in comparing multidimensional inequality; in valuing portfolios of assets or insurance policies; and in assessing systemic risk. We explore five orderings of interdependence for multivariate distributions: greater weak association, the supermodular ordering, the convex-modular ordering, the dispersion ordering, and the concordance ordering. For two dimensions, all five are equivalent, whereas for three dimensions, the first four are strictly ranked and the last two are equivalent, and for four or more dimensions, all five are strictly ranked. For the special case of binary random variables, we establish some equivalences among the orderings.

Discounting, Values, and Decisions

How do discount rates affect agents’ decisions and valuations? This paper provides a general method to analyze this question, allowing stochastic and managed cash flows, stochastic discount rates, and time inconsistency and including arbitrary learning and payoff or utility processes. We show that some of these features can lead to counterintuitive answers (e.g., “a more patient agent stops earlier”), but we also establish, under simple conditions, theorems yielding robust predictions concerning the impact of discount rates on control and stopping decisions and on valuations. We apply our theory to models of search, experimentation, bankruptcy, optimal growth, investment, and social learning.

On the smoothness of value functions and the existence of optimal strategies in diffusion models

Studies of dynamic economic models often rely on each agent having a smooth value function and a well-defined optimal strategy. For time-homogeneous optimal control problems with a one-dimensional diffusion, we prove that the corresponding value function must be twice continuously differentiable under Lipschitz, growth, and non-vanishing-volatility conditions. Under similar conditions, the value function of any optimal stopping problem is shown to be (once) continuously differentiable. We also provide sufficient conditions, based on comparative statics and differential methods, for the existence of an optimal control in the sense of strong solutions. The results are applied to growth, experimentation, and dynamic contracting settings.

A Theory of Intergenerational Altruism

Modeling intergenerational altruism is crucial to evaluate the long‐term consequences of current decisions, and requires a set of principles guiding such altruism. We axiomatically develop a theory of pure, direct altruism: Altruism is pure if it concerns the total utility (rather than the mere consumption utility) of future generations, and direct if it directly incorporates the utility of all future generations. Our axioms deliver a new class of altruistic, forward‐looking preferences, whose weight put on the consumption of a future generation generally depends on the consumption of other generations. The only preferences lacking this dependence correspond to the quasi‐hyperbolic discounting model, which our theory characterizes. Our approach provides a framework to analyze welfare in the presence of altruistic preferences and addresses technical challenges stemming from the interdependent nature of such preferences.

The Hidden Cost of Direct Democracy: How Ballot Initiatives Affect Politicians' Selection and Incentives

Citizen initiatives and referendums play an important role in modern democracies, from treaty ratifications in the European Union to gay marriage in California, to the control of foreign workers in Switzerland. Departing from the classic opposition between direct and representative democracy, we study the equilibrium effects of direct democracy institutions on the incentives and selection of elected officials. We find that facilitating direct democracy induces a negative spiral on politicians’ role and contribution to society, which may dominate any direct benefit. The theory offers predictions on reelection probabilities and politicians’ performance consistent with recent evidence from the US states.

Contract Negotiation and the Coase Conjecture: A Strategic Foundation for Renegotiation-Proof Contracts

What does contract negotiation look like when some parties hold private information and negotiation frictions are negligible? This paper analyzes this question and provides a foundation for renegotiation‐proof contracts in this environment. The model extends the framework of the Coase conjecture to situations in which the quantity or quality of the good is endogenously determined and to more general environments in which preferences are nonseparable in the traded goods. As frictions become negligible, all equilibria converge to a unique outcome which is separating, efficient, and straightforward to characterize.

From Anticipations to Present Bias: A Theory of Forward-Looking Preferences

How do future well-being and preferences affect the current well-being and preferences of forward-looking agents? Our theory explores this question, producing a new class of tractable models which capture and explain phenomena such as present bias, consumption interdependence, sign effects in discounting, and the desire to space out consumption. Agents manifest impatience toward the current period, but not necessarily toward the earlier of two future periods. The theory characterizes the well-known quasi-hyperbolic discounting model as the unique model of our class which does not display consumption interdependence. Finally, it provides a rigorous approach for analyzing the welfare of agents with time-inconsistent preferences.

Direct Democracy and Responsibility Substitution

Can direct democracy provisions improve welfare over pure representative democracy? This paper studies how such provisions affect politicians’ incentives and selection. While direct democracy allows citizens to correct politicians’ mistakes, it also reduces the incentives of elected representatives to search for good policies. This responsibility substitution reduces citizens’ ability to screen competent politicians, when elections are the only means to address political agency problems. A lower cost of direct democracy induces a negative spiral on politicians incentives, which we characterize by a disincentive multiplier. As a consequence, introducing initiatives or lowering their cost can reduce voters’ expected utility. Moreover, when elections perform well in selecting politicians and provide incentives, this indirect welfare reducing effect is stronger.