S&P 500 index inclusion no longer provides sustained price rallies for stocks, with the historical inclusion premium having largely disappeared in recent decades.

""In the last decade or two," he summarises, "the bump in stock prices from being included in the index has largely disappeared," even as the proportion of assets in index funds has surged. He adds that companies added to the S&P 500 are now more likely to underperform than outperform in the 12 months after entry."