Stock Market Glossary
Market breadth
Market breadth explained: how many shares support a trend and why advance-decline data can matter to investors.
In brief: Market breadth describes how many individual securities participate in a market move. A rising index supported by many shares is generally broader than one driven by only a few heavyweight companies.
How it works
Common measures include advancing versus declining shares, new 52-week highs and lows, and the advance-decline line. They add context to an index level, but do not replace fundamental analysis or reliably predict short-term prices.
Practical example
If an index rises while only a few large technology shares advance and most members fall, breadth is weak. That can indicate a more fragile trend. A broad recovery, in contrast, shows participation across more market segments.
What investors should keep in mind
Use breadth as context, not as a standalone buy or sell signal. The exchange, period and index weighting chosen all affect the conclusion.
