economics Paradigm Challenge

Those mutual funds that seem to beat the market aren't actually geniuses; they’re mostly just getting lucky.

March 26, 2026

Original Paper

Autopilot Alpha: Anomalies Move, Mutual Funds Follow

Roberto Stein, Arturo Rodriguez

SSRN · 6469201

The Takeaway

It is widely believed that top fund managers actively trade to capture market inefficiencies (anomalies). This study finds that 'alpha' isn't driven by clever trading, but by the stocks already in a portfolio mechanically morphing into those anomaly categories over time.

From the abstract

We test whether institutional investors intentionally exploit anomalies by decomposing changes in mutual fund factor loadings into active trading and passive mechanics - changes in the factor loadings of the stocks held in the portfolio. We replicate prior findings: funds with higher factor exposure outperform, and this advantage fades after academic publication. Yet we find no evidence of purposeful factor investment strategies. Fund exposure changes are predominantly mechanical: shifts in stoc