Rational Inattention to Discrete Choices: A New Foundation for the Multinomial Logit Modelyz Filip Matˇejka∗ and Alisdair McKay∗∗ First draft: February 2011 This draft: January 2013 Abstract Individuals must often choose among discrete alternatives with imperfect infor- mation about their values. Before choosing, they have an opportunity to study the options, but doing so is costly. This creates new choices such as the number of and types of questions to ask. We model these situations using the rational inattention approach to information frictions. We find that the decision maker's optimal strategy results in choosing probabilistically in line with a generalized multinomial logit model, which depends both on options' true values as well as on prior beliefs. Keywords: discrete choice, information, rational inattention, multinomial logit. y We thank Levent Celik, Satyajit Chatterjee, Faruk Gul, Christian Hellwig, Stepan Jurajda, Bart Lip- man, Tony Marley, Andreas Ortmann, Juan Ortner, Christopher Sims, Leonidas Spiliopoulos, Jakub Steiner, Jorgen Weibull, and Michael Woodford for helpful discussions as well as seminar participants at BU, CERGE, CREI, Harvard Institute for Quantitative Social Science, Princeton University, SED 2011, and the Toulouse School of Economics. zThis research was funded by GACRˇ P402/11/P236, GDN project RRC 11+001 and by European Re- search Council under the European Community's Seventh Framework Programme FP7/2007-2013 grant agreement N. 263790 ∗CERGE-EI, A joint workplace of the Center for Economic Research and Graduate Education, Charles University, and the Economics Institute of the Academy of Sciences of the Czech Republic. fi
[email protected] ∗∗Boston University.
[email protected] 1 1 Introduction Economists and psychologists have long known that scarce attention plays an important role in decision making (Simon, 1959; Kahneman, 1973).