Breadth Confirmation

01What it is

Breadth confirmation is the test applied at every new index high: did participation make a new high too? The advance/decline line, the percent of stocks above their 200-day average, the number of new 52-week highs — if those confirm, the crowd agrees with the index. If they do not, the high is narrow.

It is the leadership cluster's version of the Market Breadth article: the specific moment, the new high, when breadth is most informative.

02Why it exists

It exists because index highs are made by weighted prices, and weighted prices can be carried by a few names. Confirmation asks the rest of the market to vote. Historically, highs with broad confirmation have been more durable than highs without — not always, but often enough to make the check worth thirty seconds.

03How it is measured or observed

At the new high, check:

• Advance/decline lineDid it also make a new high?
• Percent above 200-dayIs it near its own recent highs, or well below?
• New highs vs new lowsAre new highs expanding and new lows scarce?
• Equal-weight and small capsRSP and IWM near their own highs?

04How professionals read it

Professionals run the check and then hold it lightly. A confirmed high raises confidence; an unconfirmed one raises the cost of being wrong. Neither is a trigger. The unconfirmed high becomes meaningful when it repeats — a series of index highs with breadth making lower highs each time is the classic narrowing pattern.

They also apply it in reverse at new lows: an index low that fewer stocks participate in (new lows contracting, A/D line holding above its prior low) is a sign the selling is exhausting.

05What strength looks like

A confirmed high: the index and the A/D line make new highs together; percent above the 200-day is high; new highs expand. The crowd agrees.

06What weakness looks like

An unconfirmed high: the index makes a new high; the A/D line makes a lower high; percent above the 200-day falls; new lows creep up. The giants agree with the index; the crowd does not.

07What it means for an investor

For an investor the check is context: an unconfirmed high is a concentrated market, which is worth knowing about a holding but rarely worth acting on.

08What it means for a trader

For a trader a confirmed high is an environment in which breakouts have the crowd behind them; an unconfirmed one is an environment in which they fail more often. It feeds the day's size and setup selection.

09What it cannot tell you

• Unconfirmed highs can persist for months; the check is not a timer.
• Breadth measures disagree with each other; mixed is a valid reading.
• A single confirmed or unconfirmed high is weak evidence; a series is stronger.

10What is happening right now

How to check this yourself today

• Find SPY's most recent high.
• Check whether the NYSE A/D line made a high in the same week.
• Compare the percent of S&P stocks above their 200-day with its level at the prior high.

11Visual market example

Confirmed, then not: the first highs are joined by breadth; later ones are not. The index chart is a single rising line. The confirmation check is the only thing that distinguishes its two halves.

12Test your understanding

Read the chart the way you would before a trade. Pick the answer, then read why.

13Key takeaways

1. At every new high, ask whether breadth made a new high too.
2. Confirmed highs are more durable; unconfirmed ones are fragile.
3. A series of unconfirmed highs is the narrowing pattern.
4. The check works in reverse at lows: contracting new lows mean exhaustion.

14Related concepts

• Market OverviewMarket Breadth
• Market OverviewLarge-Cap Leadership
• Market OverviewSmall-Cap Participation
• Major Indexes & ETFsS&P 500 / SPY

15Learn it in class