The logic of collective belief

Many political failure arguments implicitly assume that voters are irrational. This article argues that this assumption is both theoretically and empirically plausible: in politics, rationality, like information, is a collective good that individuals have little incentive to supply. In consequence, voters are frequently not only rationally ignorant but also 'rationally irrational'. Rational irrationality leads to both demand-side and supply-side political failures: competition not only pressures politicians to act on voters' biased estimates, but selects for politicians who genuinely share those biases. The analytical framework also sheds new light on log-rolling, political shirking and advertising, and politicians' human capital.