The Index Effect: How S&P 500 Additions Move Stocks
How S&P 500 inclusion moves a stock: the pre-announcement drift, run-up to effective date, decay after, and why the effect has shrunk since 2010.
index effect
S&P 500 Inclusion: What Really Happens When a Stock Joins
How a stock actually gets added to the S&P 500, what the historical “index effect” was, and why recent research finds that pop has largely vanished.