Postdoctoral Fellow, Santa Fe Institute
Visiting Scholar, Stanford University
Extramural Fellow, Tilburg University
Working Papers
1. Do You Think About What I Think you Think? Finite Belief Hierarchies in Games, December 2009. Under revision.
Abstract. The decision-theoretic approach to game theory requires players to have beliefs about all relevant uncertainty, including beliefs about other players' beliefs, and so on, which naturally leads to infinite hierarchies of beliefs. However, players may not be able to “reason all the way.” This paper constructs finite belief hierarchies by assuming that players' language is too coarse to reason about higher-order events. In the current framework, it is possible for a player to believe that other players are as least as sophisticated as he is, something which is not possible in other models of limited depths of reasoning.
2. Robustness of Equilibria in Anonymous Local Games, Revised February 2010 (subsumes Beliefs in Network Games and Convergence of Beliefs in Bayesian Network Games). Submitted
Abstract. This paper studies the robustness of symmetric Bayesian equilibria in anonymous local games to small changes in prior beliefs. Anonymous local games model strategic settings where interactions are anonymous and a player's payoffs may depend only on a subset of players, as in situations with heterogeneous externalities or in network games. If robustness is only required to hold for this subclass of games, weaker conditions suffice if the interaction structures are sufficiently sparse in a well-defined sense. In particular, approximate common belief is no longer necessary, so that the conditions do not become stronger as the number of players grows.
3. Inequality and Network Structure, joint with Garud Iyengar, Rajiv Sethi, and Sam Bowles, August 2008 (revised August 2009). Submitted.
Abstract. We consider a setting where players on a network jointly generate some value. The degree of inequality in the distribution of the value that can be sustained is determined by the opportunities for players to secede from the network. Under the natural assumption that players can only form a coalition with those in their close proximity in the network, we show that the maximum degree of inequality that can be sustained is directly linked to the size of a maximum independent set of a network, a measure for the sparseness of the network.
4. Strategic Achilles: Is prior information about your opponent's strategy valuable?, joint with John H. Miller, and Ariana Strandburg-Peshkin. July 2009. Submitted.
Abstract. Is having prior information about your opponent's strategy helpful? We investigate this question using an adaptive framework where agents must implement their strategies as finite automata. We show that agents who are informed about the strategic complexity of their opponent do worse than their uninformed opponents in games like Battle of the Sexes and Chicken. Intuitively, it is not so much the ability of uninformed agents to commit to a certain strategy, but the inability of the informed agents to commit not to use their information that gives the uninformed agents a strategic advantage in these games.
5. Congestion, equilibrium and learning: The minority game, joint with Mark Voorneveld, CentER Discussion Paper (2007) (revised July 2009). Submitted.
Abstract. The minority game is a simple congestion game. As the set of equilibria for the game is large, a natural question is which equilibrium will be selected by the players. We show that many standard learning processes do not converge to the unique symmetric mixed strategy equilibrium which is arguable focal in this game, but in fact converge to distinct equilibria.
6. The minority game: An economics perspective, CentER Discussion Paper (2007) (revised November 2008). Submitted.
Abstract. This paper gives a critical account of the literature on the minority game, a simple congestion game which has been studied using nontraditional learning models, and relates the learning process considered in this literature to standard learning models in economics. It compares the theoretical predictions of the literature to experimental results on the minority game and related games.
Publications
1. Random intersection graphs with a tunable degree distribution and clustering, joint with Mia Deijfen, Probability in the Engineering and Informational Sciences, volume 23, issue 04, pp. 661-674 (2009).
This paper is written for a mathematics journal. A version that more easily accessible for an economics audience can be found here (Chapter 5 of my dissertation, see below).
2. Learning to be prepared, joint with Mark Voorneveld, International Journal of Game Theory 37, pp. 333-352 (2008).
3. An axiomatization of minimal curb sets, joint with Mark Voorneveld and Henk Norde, International Journal of Game Theory 33, pp. 479 - 490 (2005).
4. Free trade and its enemies, joint with Paul Tang, De Economist, 152 - 153, pp. 427 - 437 (2004).
Dissertation
My dissertation, Networks and Learning in Game Theory can be downloaded here. If you would like to receive a copy by mail, please contact me at willemien.kets (at) gmail.com .
Publications in physics
1. Zn- and Cd-induced features at the GaAs(110) and InP(110) surfaces studied by low-temperature scanning tunneling microscopy, joint with Randy de Kort, Maurice van der Wielen, André van Roij, and Herman van Kempen, Physical Review B, 63, 125336 (2001).
Press coverage
How to turn a herd on Wall Street?, New York Times, April 6, 2008.