Why Do Defaults Affect Behavior? Experimental Evidence from Afghanistan

By Joshua Blumenstock, Michael Callen, Tarek Ghani We report on an experiment examining why default options impact behavior. By randomly assigning employees to different varieties of a salary-linked savings account, we find that default enrollment increases participation by 40 percentage points—an effect equivalent to providing a 50% matching incentive. We then use a series of experimental interventions to differentiate between explanations for the default effect, which we conclude is driven largely by present-biased preferences and the cognitive cost of thinking...