Aaron Brown, Columnist

We Still Need to Find Out Why Stocks Gains Come at Night

The market anomaly of overnight drift has baffled researchers and potentially put retail investors at a disadvantage.

March 17, 2025 at 9:00 AM UTC

Aaron Brown is a former head of financial market research at AQR Capital Management. He is also an active crypto investor, and has venture capital investments and advisory ties with crypto firms. He is the author of the soon-to-be-released "Wrong Number."

Puzzling markets.
Photographer: Michael Nagle/Bloomberg

Provide news feedback or report an error

Site feedback:

Take our Survey

This article is for subscribers only.

The tendency of stocks to produce all their gains at night, when markets are closed, and systematically lose money during the daylight hours, has baffled researchers for four decades and potentially put retail investors at a disadvantage.

The debate over what drives this behavior will surely be revived by the award of the prestigious Harry Markowitz prize for the best paper of the year in investment management to Victor Haghani, Vladimir Ragulin and Richard Dewey for “Night Moves: Is the Overnight Drift the Grandmother of All Market Anomalies?”