For decades, joining the S&P 500 was considered a gift to a company’s shareholders. A stock’s price would typically jump upon entering the index, as demand from funds tracking the S&P 500 increased. This phenomenon, often referred to as the “inclusion pop,” was once one of the market’s more reliable anomalies. Yet this effect has gradually faded, even as the assets tracking the index have grown significantly. The real story, however, is more interesting than simply asking whether the inclusion pop still works or is dead. While the initial price surge may have weakened, inclusion continues to change a company in meaningful and lasting ways. In this article, we’ll explore what actually changes after a company joins the S&P 500, why the inclusion pop has faded, and whether the phenomenon is truly dead. The classic story The original logic was straightforward. Funds tracking the S&P 500 are required to hold every constituent, so when a company is added to the index,...