  I study costly information acquisition in a two-sided matching problem, such
as matching applicants to schools. An applicant's utility is a sum of common
and idiosyncratic components. The idiosyncratic component is unknown to the
applicant but can be learned at a cost. When applicants are assigned using an
ordinal strategy-proof mechanism, too few acquire information, generating a
significant welfare loss. Affirmative action and other realistic policies may
lead to a Pareto improvement. As incentives to acquire information differ
across mechanisms, ignoring such incentives may lead to incorrect welfare
assessments, for example, in comparing a popular Immediate Assignment and an
ordinal strategy-proof mechanism.
