S&P 500 Index — What It Is, How It’s Calculated, Market Concentration Risk, and Smarter Ways to Track It
S&P 500 index is the benchmark most U.S. investors watch — and, in 2025, it’s also a lesson in concentration risk. Below, you’ll get a plain-English explainer of how the index is built, why a handful of mega-caps can swing it so dramatically, how equal-weight variants change the picture, and what today’s market structure means … Read more