The Index Effect Minute by Minute: Intraday Returns at NASDAQ-100 and MSCI U.S. Rebalancings

Abstract

I use intraday data from 2013 to 2017 and a dataset of NASDAQ-100, MSCI USA and MSCI USA Small Cap Index constituent changes to investigate abnormal returns and trading volume around index rebalancings. The results show no pre-announcement speculation but a significantly positive (negative) post-announcement jump followed by an intraday drift for promotions (demotions). For small-cap changes, the post-announcement jump is smaller but abnormal returns with the same sign are also found on the rebalancing date and especially during the last 30 minutes of trading. Large-cap index changes have higher abnormal trading volume but much smaller abnormal returns on the rebalancing date. Consistent with the price pressure hypothesis, I find a reversal during the early trading hours on the day following the rebalancing date.