S&P 500 Index Composition and Concentration Analysis
Scraped and cleaned S&P 500 constituent data (Wikipedia, yfinance); analyzed sector weight vs. company count and 10-year sector ETF returns. Measured concentration with the Herfindahl-Hirschman Index (HHI): top 10 holdings hold about 40% of index weight and the HHI runs about 10x the equal-weight baseline.

