Ticker&TapeMarket breadth: how many stocks join the move
An index can rise while most stocks fall. Breadth measures how many stocks take part in a move, and it often warns you before the index does.
What breadth means
Big indexes like the S&P 500 are weighted by market value, so a handful of giant companies can carry the index higher on their own. Breadth looks at all stocks equally and asks: how many are actually going up?
A broad rally, with most stocks rising, is healthy and gives you many good setups. A narrow rally, led by a few big names while most stocks lag, is fragile and often ends sooner.
Percent of stocks above the 50 and 200-day
This shows the share of stocks trading above their 50-day and 200-day moving averages. Above about 70% means strength is widespread, but the market can be stretched in the short term. Below about 30% means most stocks are weak, often near the late stage of a correction.
Watch the direction too. If the index makes a new high while fewer stocks stay above their 50-day, the rally is narrowing.
New highs vs new lows
Count the stocks making new 52-week highs and compare them with those making new lows. In a healthy uptrend, new highs clearly outnumber new lows. When the index climbs but new highs shrink and new lows grow, it is a warning sign.
Advance/decline line and McClellan
Both appear on the Market breadth page next to the distribution-day count.
- Advance/decline (A/D) line: a running total of advancing stocks minus declining stocks each day. A rising A/D line confirms the index; an index at new highs with a falling A/D line is a negative divergence.
- McClellan oscillator: a measure of the short-term momentum of advances minus declines. Readings far above zero show strong, broad buying; deep negative readings show heavy selling and often appear near short-term lows.
Equal weight vs cap weight
A quick test is to compare an equal-weight S&P 500 ETF (RSP) with the regular, cap-weighted one (SPY). On the Compare page, plot the ratio RSP:SPY. A rising ratio means the average stock is doing better than the giants, so participation is broad. A falling ratio means a few big stocks are doing the work.
How to use breadth
Breadth is a confirming tool. Use it alongside market direction and distribution days, not as a timing signal on its own. When price and breadth agree, you can trade with more confidence; when they diverge, reduce risk.
Common mistakes
- Trusting an index at new highs without checking how many stocks are participating.
- Using one breadth reading as an exact buy or sell signal.
- Shorting just because breadth looks stretched in a strong uptrend.
Key points
- Breadth measures how many stocks join a move; broad rallies are healthier.
- Watch for divergences: index up while breadth weakens is a warning.
- Use RSP:SPY, new highs vs lows and the A/D line to confirm the market's trend.
Check what you learned
Answer at least 2 of 3 correctly to complete the lesson.
1. The S&P 500 makes a new high, but fewer stocks are above their 50-day line and the A/D line is falling. What does that suggest?
Cap-weighted indexes can be carried by a few giants. When the index rises while breadth weakens, the move is fragile.
2. On the Compare page, the RSP:SPY ratio is rising. What does that mean?
RSP is the equal-weight S&P 500 and SPY the cap-weighted one. A rising ratio means the typical stock is keeping up.
3. How should breadth be used?
When price and breadth agree you can trade with more confidence; when they diverge, reduce risk.
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