Biased Voters, Social Information, and Information Aggregation Through Majority Voting1

We experimentally investigate information aggregation through majority voting when some vot-ers are biased. In such situations, majority voting can have a dark side, i.e. result in groups making choices inferior to those made by individuals acting alone. We develop a model to pre-dict how two types of social information shape e ¢ ciency in the presence of biased voters and we test these predictions using a novel experimental design. In line with predictions, we \u85nd that information on the popularity of policy choices is bene\u85cial when a minority of voters is biased, but harmful when a majority is biased. In theory, information on the success of policy choices elsewhere de-biases voters and alleviates the ine ¢ ciency. In the experiment, providing socia