An index can rise while most stocks fall, if a few heavyweights do the lifting. Market breadth looks past the index number to ask: how many stocks are actually participating?
Advancers vs decliners
The simplest breadth measure counts advancing stocks (closed up) against declining stocks (closed down). The advance–decline (A/D) ratio divides one by the other.
- Broad strength — far more advancers than decliners: the rally is widespread.
- Narrow strength — the index is up but decliners lead: the move is concentrated in a few names and may be less durable.
Why it’s useful
Breadth adds nuance the index alone can hide. A market making new highs on shrinking breadth is worth a second look; a sell-off where breadth is already improving may be losing steam.
The dashboard’s Market Breadth panel shows the live advancers/decliners split and the share of equities that are green — a quick read on how broad the day’s move is.