Survivorship Bias
Specifically in the context of mutual funds, the tendency for poor performers to drop out while strong performers continue to exist. This results in an overestimation of past returns.
Investopedia Commentary
For example, a mutual fund company's selection of funds today will include only those that have been successful in the past. Many losing funds are closed and merged into other funds to hide poor performance. This is an important issue to take into account when analyzing past performance.
Also known as "survivor bias."
Related Links
The Truth Behind Mutual Fund Returns
See also: Mutual Fund, Window Dressing