What Is Market Breadth?
Breadth tells you whether the index move is being carried by the whole market or only a narrow group of leaders.
Market breadth measures how widely participation is spread across stocks, sectors, or exchanges. It helps answer whether an index rally is broad and durable or narrow and fragile.
Breadth matters because headline index strength can hide weak participation underneath. If only a few mega-cap names are lifting the tape, the move can look healthier than it actually is.
- Watch advance-decline behavior alongside the index itself.
- Compare equal-weight vs cap-weight performance to spot concentration risk.
- Track whether new highs are expanding or shrinking during rallies.
- Check whether sector participation is broad or limited to one leadership pocket.
- Use breadth as confirmation, not as a standalone trade trigger.
- Recheck breadth after major macro prints and earnings clusters.
- Assuming the S&P 500 tells the full story by itself.
- Reading one breadth indicator in isolation without price context.
- Calling every narrow rally dangerous without checking the regime.
Use it inside Meridian
All glossary →Related Academy modules
Academy →Build the baseline language for trends, volatility, catalysts, and why a stock deserves attention in the first place.
Connect inflation, rates, PMI, labor data, and the yield curve to what actually changes in sector leadership.
Move from indicator collecting to actual scenario planning with triggers, invalidation, and alternative outcomes.
Common questions
2 answersWhy can breadth weaken while the index rises?
Because a small number of very large stocks can lift a cap-weighted index even while many smaller names lag or fall.
Does weak breadth always mean a sell-off is coming?
No. Weak breadth is a warning about concentration, not a timing signal by itself. It becomes more important when price structure also starts to weaken.
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