What economic theory suggests that voters choose not to become informed due to the cost?

Rational ignorance theory suggests that voters may choose not to become fully informed because researching political issues costs more than the expected benefit.

The logic is especially strong in large elections. An individual vote has only a small chance of changing the result, so the personal payoff from mastering every policy detail may be tiny compared with the time and effort required. Remaining uninformed can therefore be a calculated response to incentives rather than proof that voters are unintelligent or indifferent.

The term was coined by economist Anthony Downs in his 1957 book An Economic Theory of Democracy. In practice, voters may use shortcuts such as party labels, endorsements, past performance, trusted commentators, or a few salient issues. These methods reduce information costs, though they can also make voters vulnerable to misleading signals and strategic campaigning.

Rational ignorance is associated with public choice economics, but it is not identical to public choice theory as a whole. Nor is it the same as Arrow's impossibility theorem or the median voter theorem, which address different problems in collective decision-making. The theory also predicts that people may become more informed when an issue feels personally important or when the expected consequences are large.