Market Breadth
The share of index members participating in a move. Tells you whether a rally is broad-based or narrow.
Market breadth measures how many stocks in an index are participating in a move, as opposed to how many index points the move covers. Two indices with the same daily return can be very different markets — one where 80% of constituents rose, and one where 5 mega-cap stocks rose while the rest fell.
The metrics MarketGrep uses
- % above 20-day moving average — short-term participation. Above 70% = healthy short-term uptrend; below 30% = oversold.
- % above 50-day moving average — intermediate-term participation. The headline breadth metric on most desks.
- % above 200-day moving average — long-horizon trend gauge. Crossing below 50% historically marks the move from bull to bear regime.
- Advance–decline ratio — daily count of advancing vs declining issues; sensitive to small caps.
Why it matters
Narrow rallies — a few mega-caps lifting the index while breadth deteriorates — historically precede corrections. Broad rallies are more durable. Breadth divergence (price making new highs while breadth fails to confirm) is one of the cleanest tape-warning signals.
Related
MarketGrep is a market-environment dashboard. Every signal on this page is descriptive, not prescriptive — there is no buy or sell recommendation anywhere on the site. Data is for informational purposes only and may be delayed, inaccurate, or revised.