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Breadth answers one question: are most stocks moving with the index, or is a small group of names doing all the work? A market that goes up on five mega-caps is more fragile than a market that goes up on four hundred names. Breadth tells you which kind of day it was.

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The metrics you’ll see

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Advances / Declines (A/D)

How many stocks went up vs down. Net A/D = advancers minus decliners.
  • Strongly positive (e.g., +300) = broad rally, real participation
  • Strongly negative = broad sell-off
  • Near zero on a big index move = only a few names moved the index

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% above moving average

What fraction of stocks are above their 1W / 1M / 3M / 6M / 1Y MA. Stacked across timeframes:
  • % above 1W MA = short-term momentum
  • % above 1M MA = trend health
  • % above 1Y MA = secular regime
The shorter the MA, the more sensitive — when % above 1W drops sharply but % above 1Y stays high, you’re in a tactical pullback inside a structural uptrend.

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RSP / SPY ratio

Equal-weight S&P (RSP) divided by cap-weighted (SPY).
  • Falling RSP/SPY = mega-caps carrying the index, narrow leadership
  • Rising RSP/SPY = broad participation, healthy rally

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”Deteriorating breadth”

When you read this in a recap, it usually means one of:
  • A/D net is shrinking even as the index goes up
  • % above 1M or 3M MA is falling toward 50%
  • RSP/SPY is dropping (concentration is increasing)
Why it matters: deteriorating breadth often precedes corrections. The index can stay green for weeks while internals rot, and then catch up suddenly.

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Where you see it

  • Equity Internals section of the Daily Recap
  • Market Pulse breadth tile
  • The Indices page surfaces a US breadth panel