A bias (distortion) that results from the decision of a hedge fund whether to report its results (returns or performance) to a database or not. It is up to each hedge fund to opt for reporting or not. A fund can also choose the database in which it will be included. Individual databases differ substantially in terms of size and composition. Self-selection bias comes in two subgroups: self-selection bias I and self-selection bias II. The self-selection bias (I) exemplifies the situation before a hedge fund is included in the database, while the self-selection bias (II) refers to the situation after the is fund included in the database.

Self-selection bias is also known as self-reporting bias.