Correlated Equilibrium via Hierarchies of Beliefs

We study a model of correlated equilibrium where every player takes actions based on his hierarchies of beliefs (belief on what other players will do, on what other players believe about others will do, etc.) intrinsic to the game. Our model does away with messages from outside mediator that are usually assumed in the interpretation of correlated equilibrium. We characterize in every finite, complete information game the exact sets of correlated equilibria (both subjective and objective) that can be obtained conditioning on hierarchies of beliefs; the characterizations rely on a novel iterated deletion procedure. If the procedure ends after k rounds of deletion for a correlated equilibrium obtained from hierarchies of beliefs, then players in the equilibrium need to reason to at most k-th order beliefs. Further conceptual and geometric properties of the characterizations are studied.game theory; correlated equilibrium; higher order beliefs; purification; intrinsic correlation

What is the Optimal Trading Frequency in Financial Markets?

This paper studies the impact of increasing trading frequency in financial markets on allocative efficiency. We build and solve a dynamic model of sequential double auctions in which traders trade strategically with demand schedules. Trading needs are generated by time-varying private information about the asset value and private values for owning the asset, as well as quadratic inventory costs. We characterize a linear equilibrium with stationary strategies and its efficiency properties in closed form. Frequent trading (more double auctions per unit of time) allows more immediate asset reallocation after new information arrives, at the cost of a lower volume of beneficial trades in each double auction. Under stated conditions, the trading frequency that maximizes allocative efficiency coincides with the information arrival frequency for scheduled information releases, but can far exceed the information arrival frequency if new information arrives stochastically.  A simple calibration of the model suggests that a moderate market slowdown to the level of seconds or minutes per double auction can improve allocative efficiency for assets with relatively narrow investor participation and relatively infrequent news, such as small- and micro-cap stocks

What is the Optimal Trading Frequency in Financial Markets?

This paper studies the impact of increasing trading frequency in financial markets on allocative efficiency. We build and solve a dynamic model of sequential double auctions in which traders trade strategically with demand schedules. Trading needs are generated by time-varying private information about the asset value and private values for owning the asset, as well as quadratic inventory costs. We characterize a linear equilibrium with stationary strategies and its efficiency properties in closed form. Frequent trading (more double auctions per unit of time) allows more immediate asset reallocation after new information arrives, at the cost of a lower volume of beneficial trades in each double auction. Under stated conditions, the trading frequency that maximizes allocative efficiency coincides with the information arrival frequency for scheduled information releases, but can far exceed the information arrival frequency if new information arrives stochastically.Asimple calibration of the model suggests that a moderate market slowdown to the level of seconds or minutes per double auction can improve allocative efficiency for assets with relatively narrow investor participation and relatively infrequent news, such as small- and micro-cap stocks

Bilateral trading in divisible double auctions

Existing models of divisible double auctions typically require three or more traders—when there are two traders, the usual linear equilibria imply market breakdowns unless the traders’ values are negatively correlated. This paper characterizes a family of nonlinear ex post equilibria in a divisible double auction with only two traders, who have interdependent values and submit demand schedules. The equilibrium trading volume is positive but less than the first best. Closed-form solutions are obtained in special cases. Moreover, no nonlinear ex post equilibria exist if: (i) there are n≥4 symmetric traders or (ii) there are 3 symmetric traders with pure private values. Overall, our nonlinear equilibria fill the “n=2” gap in the divisible-auction literature and could be a building block for analyzing strategic bilateral trading in decentralized markets. Keywords: Divisible double auctions; Bilateral trading; Bargaining; Ex post equilibriu

Correlated Equilibrium via Hierarchies of Beliefs

We study a model of correlated equilibrium where every player takes actions based on his hierarchies of beliefs (belief on what other players will do, on what other players believe about others will do, etc.) intrinsic to the game. Our model does away with messages from outside mediator that are usually assumed in the interpretation of correlated equilibrium. We characterize in every finite, complete information game the exact sets of correlated equilibria (both subjective and objective) that can be obtained conditioning on hierarchies of beliefs; the characterizations rely on a novel iterated deletion procedure. If the procedure ends after k rounds of deletion for a correlated equilibrium obtained from hierarchies of beliefs, then players in the equilibrium need to reason to at most k-th order beliefs. Further conceptual and geometric properties of the characterizations are studied

A Note on Intrinsic Correlation

In this note we characterize the strategic implication of intrinsic correlation, introduced by Brandenburger and Friedenberg (2008), in the subjective correlated equilibrium setting of a complete information game. Intrinsic correlation restricts correlation devices to variables within the game, i.e. players's beliefs (and higher order beliefs) about each other's strategies, in contrast to signals or sunspots from the "outside." The characterization is a strengthening of best-response set with an injectivity condition for a certain subset identified by an iterative procedure. We also give an iterative procedure, analogous to the iterated removals of dominated strategies, that arrives at strategies consistent with our characterization, which always exist

A Note on Intrinsic Correlation

In this note we characterize the strategic implication of intrinsic correlation, introduced by Brandenburger and Friedenberg (2008), in the subjective correlated equilibrium setting of a complete information game. Intrinsic correlation restricts correlation devices to variables within the game, i.e. players's beliefs (and higher order beliefs) about each other's strategies, in contrast to signals or sunspots from the "outside." The characterization is a strengthening of best-response set with an injectivity condition for a certain subset identified by an iterative procedure. We also give an iterative procedure, analogous to the iterated removals of dominated strategies, that arrives at strategies consistent with our characterization, which always exist

Correlated Equilibrium via Hierarchies of Beliefs

We study a model of correlated equilibrium where every player takes actions based on his hierarchies of beliefs (belief on what other players will do, on what other players believe about others will do, etc.) intrinsic to the game. Our model does away with messages from outside mediator that are usually assumed in the interpretation of correlated equilibrium. We characterize in every finite, complete information game the exact sets of correlated equilibria (both subjective and objective) that can be obtained conditioning on hierarchies of beliefs; the characterizations rely on a novel iterated deletion procedure. If the procedure ends after k rounds of deletion for a correlated equilibrium obtained from hierarchies of beliefs, then players in the equilibrium need to reason to at most k-th order beliefs. Further conceptual and geometric properties of the characterizations are studied