Stocks receiving an S&P 500 berth have generated an average 4-percentage-point gain over the equal-weight S&P 500 on the day their inclusion was announced since 2021, with 74 percent of new entrants beating the broader benchmark, according to market-performance data compiled by analysts. Roughly 4 percent of the index—about 20 companies—turns over each year. Eight additions have already been announced in 2025, and analysts note that the largest price pops increasingly coincide with heavy retail trading activity, often before the inclusion becomes public. The retail bid itself is intensifying. A Goldman Sachs trading desk said the 10-day average share of retail orders in loss-making technology stocks climbed to a record 23 percent and reached 25 percent this week, underscoring the influence of individual investors on short-term index-related moves.