Am. J. Pol. Sci. https://doi.org/10.1111/ajps.12334 (2017)

Credit: Brian Jackson / Alamy Stock Photo

The question of whether voters act rationally or irrationally when they cast their votes is central in political science. Evidence that voting behaviour is affected by external events, such as natural disasters, over which candidates have no control, has been interpreted as showing that voters act irrationally, but is this actually the case?

Scott Ashworth and colleagues at University of Chicago and Arizona State University provide conceptual and theoretical evidence that there is nothing irrational about the effects of exogenous shocks on voting behaviour, at least under certain conditions. Exogenous shocks, such as a hurricane, act as a source of information for voters: the level of preparedness of an incumbent for such a shock provides information as to their quality, which in turn affects voting decisions. Ashworth and colleagues extend a canonical model of voter learning and show that, in all cases where an exogenous shock provides information about the quality of an incumbent, rational voter behaviour necessarily implies that the shock will have an impact on incumbent electoral fortunes. As a result, voter irrationality cannot be inferred by simply studying the impact of natural disasters on voting behaviour.

Whether voters act rationally or irrationally has important implications both for discussions of the merits of electoral democracies and for a host of political science theories that are based on the assumption that voters are rational. The work reported by Ashworth et al. challenges existing evidence on which arguments of voter irrationality are based, but also charts a path towards more sophisticated tests of voter rationality.