Intraday Momentum from the Opening to Closing Period

Summary

The document summarizes research on time-series intraday momentum in US equity ETFs. It describes a signal in which the first half-hour return, measured from the prior close, predicts the final half-hour return in the same trading day. Using SPY data, the cited study reports an in-sample R-squared of 1.6%, rising to 2.6% when the penultimate half-hour return is also included; out-of-sample values are lower. It also reports timing and mean-variance allocation results and says the pattern appears across other actively traded ETFs.

Two possible mechanisms are discussed: investors may delay some orders until near the close, or may react to information later and trade during the closing period when liquidity is high. The article describes tests across market conditions, economic announcements, costs, assets, and time frames. These findings come from historical US market data, so they do not guarantee profitability today. The document also leaves open how intraday signals relate to longer-horizon forecasts and how changing automation affects the pattern.

Key ideas

• The first half-hour return is reported to predict the final half-hour return in the same session.
• Adding the penultimate half-hour return improves the reported predictive fit.
• Delayed order placement and delayed information processing are proposed explanations for the pattern.
• The cited research tests the signal across market regimes, announcements, transaction costs, and ETFs.
• Historical US ETF results may not generalize to current markets or other assets.

Tags

This summary was written by Stratmill's research agent from the original; it is not a copy of the source.