The Disappearing Overnight Drift
In a 2021 Liberty Street Economics post, we documented the “overnight drift”—a large, persistent return to holding U.S. equity futures in the narrow window between 2:00 and 3:00 a.m. Eastern time, when European equity markets open. Five additional years of data later, that pattern appears to have faded: the 2:00–3:00 window that previously generated roughly 3.7 percent per annum has averaged close to zero since 2021. In this post, we revisit the overnight drift in light of the post-publication sample and use our inventory-risk framework to ask which of three observable channels—the dispersion of closing order imbalances, the level of return variance, or the risk-bearing capacity of liquidity providers—accounts for the change.
The Overnight Drift in U.S. Equity Returns
Since the advent of electronic trading in the late 1990s, S&P 500 futures have traded close to 24 hours a day. In this post, which draws on our recent Staff Report, we document that holding U.S. equity futures overnight has earned a large positive return during the opening hours of European markets. The largest positive returns in the 1998–2019 sample have accrued between 2 a.m. and 3 a.m. U.S. Eastern time—the opening of European stock markets—and averaged 3.6 percent on an annualized basis, a phenomenon we call the overnight drift.
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