Market Breadth

Market breadth measures how many stocks are participating in a market move—whether most stocks are rising or falling alongside the overall index. Think of it as checking if the whole team is winning together, or just a few star players carrying the load. You'll hear about it when analysts discuss market health; it matters because a strong index can hide weakness if only a handful of mega-cap stocks are driving gains while thousands of others lag. For example, if the S&P 500 hits a new high but only 30% of stocks in it are actually up on the day, that's narrow breadth—a potential warning sign. Broad breadth, where 70%+ of stocks advance, suggests a healthier, more sustainable rally.