Why Indexing Works
7 Pages Posted: 14 Oct 2015 Last revised: 8 Jan 2018
Date Written: May 10, 2017
We develop a simple stock selection model to explain why active equity managers tend to underperform a benchmark index. We motivate our model with the empirical observation that the best performing stocks in a broad market index often perform much better than the other stocks in the index. Randomly selecting a subset of securities from the index may dramatically increase the chance of underperforming the index. The relative likelihood of underperformance by investors choosing active management likely is much more important than the loss to those same investors from the higher fees for active management relative to passive index investing. Thus, active management may be even more challenging than previously believed, and the stakes for finding the best active managers may be larger than previously assumed.
Keywords: Indexing, Passive Management, Active Management
JEL Classification: G10, G11
Suggested Citation: Suggested Citation