Overview
A stock index can be dragged higher by a few giant names while most stocks quietly weaken. Market breadth looks under the hood: it measures how many stocks are actually participating in a move, giving an early read on whether a trend is healthy or hollow.
The breadth gauges
- A/D LINEAdvance/Decline line — a running total of advancing minus declining stocks. Confirms or diverges from the index.
- TICKNYSE TICK — net up-ticking minus down-ticking stocks right now; a short-term gauge of intraday pressure and extremes.
- NEW HIGHS-LOWSNew highs vs new lows — how many stocks make 52-week highs vs lows; a read on participation.
- % ABOVE MA% above a moving average — the share of stocks above, say, their 50-day MA; a breadth-of-trend gauge.
Why it matters
Breadth is the difference between a broad, durable advance and a narrow, fragile one. When the A/D line, new-high count, and % of stocks above their moving averages all confirm an index high, the move has participation. When the index rises but breadth fades, leadership is narrowing — a warning that risk is building under a calm surface.
Honest assessment
What breadth reveals
- Whether a rally is broad or narrow.
- Early warning when leadership thins.
- Intraday extremes (via TICK).
Its limits
- Divergences can last a long time.
- Not a precise timing tool.
- Index composition can distort it.
Breadth is a context and risk gauge, not a precise trigger — divergences warn, but can persist for a long time before resolving.
Practice
The index makes a new high but the A/D line doesn't. What is that?
A bearish breadth divergence — the index is being carried by fewer stocks, a sign the advance is narrowing and may be fragile.
What does market breadth measure?
Participation — how many stocks are taking part in a move, not just where the index (often a few big names) is.
Is a single breadth reading a timing signal?
No — breadth is context. Divergences can persist; use it to gauge the health of a move, confirmed by price.
This concept in the knowledge graph
Resources
- CONCEPTSector rotation — the other big-picture lens.
- CONCEPTRelative strength — leadership within breadth.
References
- Market breadth & the advance/decline line — Investopedia.
- Breadth indicators — StockCharts.