Radar Perene / Articles / concept

What is market breadth?

Concept

There are two questions hidden in every trading session, and the index answers only the first. How much did the market move — that, the needle tells at once. How many stocks took part in the move — that, it keeps quiet, because the largest companies weigh more and speak louder. Market breadth is the second question: checking whether the majority of stocks backs what the average announces — or merely lends it a name.

"How much" is not "how many." A market walking whole in one direction and a market dragged along by a handful of giants print the same number on the screen — but they are not the same market. In the first, the index represents; in the second, it disguises. It is the difference between a choir and a soloist with a microphone: from a distance, the volume deceives. That is why the archive records both things — where the index went and how many went along — and does not file the two markets under the same name.

The case in the middle. The same logic applies to price. Rather than accept the average, which the giants pull toward wherever they stand, the house looks at the median: if every stock stood in a line, from cheapest to dearest, the case in the middle is the one at the very center. It is the price of the typical stock — a portrait of the majority, immune to the size of any neighbor. Average and median usually agree; when they diverge, the divergence is the news.

What breadth is not. It is not a trigger. When most stocks turn cheap while the index stays on its feet, breadth records the disconnect — it does not set a time for the reunion. Broad markets narrow, narrow markets broaden, and no entry knows in advance which it will be. Breadth says how many support what the index claims; the rest is observation. The arithmetic lives in the house's methodology; the entry keeps the second question.

Related episodes: the concept at work in the archive: "Sixty-three percent of stocks trade below fair value, the IBOV's median P/E stands at 10.93 (…) It is a market where price has already retreated, but the mood has not followed" (Daily, June 29, 2026). In scene: Cheap on multiples, stretched on risk. See also: What is a statistical anomaly · What is the Ânima Index · The bottom is not where fear screams →

Read also: What is a statistical anomaly? · What is the Ânima Index? · The bottom is not where fear screams — it is where the floor stops giving way · Cheap on multiples, stretched on risk

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