Palantir Technologies, Dell Technologies, and Erie Indemnity will join the S&P 500 index effective before the market opens on September 23, 2024, replacing American Airlines, Etsy, and Bio-Rad Laboratories. The announcement led to significant after-hours trading gains for all three companies, with Palantir rising nearly 8%, Dell increasing by about 6-8%, and Erie by approximately 3-5.5%. The inclusion of these companies in the S&P 500 reflects a broader market trend towards technology and artificial intelligence-related firms. Conversely, the removal of American Airlines underscores the airline industry's recent struggles, including delayed plane deliveries and rising labor costs. This quarterly rebalance aims to ensure the indices better represent their respective market capitalization ranges.