Summary:
- Interactive Brokers, a major online brokerage firm, will be joining the S&P 500 index, replacing Walgreens Boots Alliance.
- The S&P 500 is a stock market index that tracks the performance of the 500 largest publicly traded companies in the United States.
- This change reflects the growing importance of online trading platforms and the shift away from traditional brick-and-mortar retail companies in the stock market.