Market breadth — advance/decline, % above MA

The Nifty prints a fresh all-time high. The news says "markets scale new peak." It feels, reasonably, like good news — the tide is rising, most boats must be lifting with it.

But an index is a weighted average of its members, and a weighted average can lie about the crowd it summarises. A handful of the largest companies, if they rise enough, can drag the headline number to a new high while the typical stock is quietly falling. The index says "up." Most of the market, underneath, might be saying "down."

So the honest question is not "did the index go up?" It is: how many stocks actually took part? A rally powered by five hundred rising stocks and a rally powered by five rising giants can produce the identical index high — and they are not the same market at all. This module is about reading the crowd behind the headline. That reading is called breadth.

Market breadth is any measure of how many stocks are participating in a market move, rather than how far the index travelled. It exists because the index alone is a headline that can be written by a few loud voices.

Think of the index as the captain's report and breadth as a headcount of the crew. The captain can announce "we are making great progress" while, below deck, most of the crew has stopped rowing and only the four strongest are still pulling. For a while the ship still moves forward — the strong four are powerful. But a boat propelled by four rowers instead of two hundred is far easier to stall. If any one of those four tires, progress falters badly.

That is the entire intuition. A broad advance — most stocks rising together — rests on many legs and is hard to knock over. A narrow advance — a few heavyweights carrying a tiring majority — rests on few legs and is fragile. Nothing about breadth predicts when a narrow rally ends. It tells you how much support is underneath it if trouble arrives. Breadth is a measure of the foundations, read while the building still stands.

In India this matters especially because the headline indices are top-heavy. A small number of very large companies carry a large share of the Nifty's weight. It is entirely possible for those few to lift the index while the broader market — the mid-caps and small-caps most retail investors actually own — is already in a quiet decline. Watching only the Nifty, you would never see it.

Breadth is measured in several simple ways. Two are worth knowing well.

The advance/decline line. Each day, count how many stocks in a market rose (advances) and how many fell (declines). Subtract declines from advances to get the day's net figure — say, +300 or −150. Then keep a running total, adding each day's net to the day before. That running total is the advance/decline line. When it rises, more stocks are going up than down day after day — participation is broadening. When it falls, the average stock is losing ground even if the index is not.

The single most useful thing the A/D line does is confirm or contradict the index. If the index makes a new high and the A/D line makes a new high with it, the rally is broad and confirmed. If the index makes a new high but the A/D line makes a lower high, that is a breadth divergence — the headline climbed but fewer stocks came along.

The percentage above a moving average. A moving average is simply the average closing price over the last N days, recalculated each day, which smooths out the daily noise into one slow line — the 200-day average is a common stand-in for a stock's long-term trend. Now ask: of all the stocks in the market, what share are trading above their 200-day average? If 75% are, most stocks are in long-term uptrends — a healthy, broad market. If that figure has slid to 35% while the index is still near its high, most stocks have already rolled over and only the giants are holding the headline up.

The chart below shows the classic warning shape: the index pushing to a new high on top, while the participation measure beneath it makes a lower high.

Read the two panels above as one story. illustrative

Over the first stretch, the index climbs to its first peak and the advance/decline line climbs right alongside it. This is a confirmed advance: the headline is rising because most stocks are rising. Whatever is driving the market is lifting the crowd, not just the captains. If you owned a spread of stocks here, most of them would be working.

Then something changes. The index dips, recovers, and pushes to a second, higher peak — a fresh new high, the kind that makes headlines. But look beneath it. The advance/decline line, over the exact same stretch, makes a lower second peak. The dashed lines make the split visible: the index line tilts up, the participation line tilts down. The market got to a new high on fewer rising stocks. The heavyweights carried it; the average stock stayed behind.

The honest read is not "sell everything." It is a change in posture: this rally is narrowing; it now rests on fewer legs; the margin of safety underneath it has shrunk. You might tighten stops, slow new buying, or simply raise your alertness. What you should not do is treat the divergence as a countdown clock. Breadth shifts the odds toward fragility; it does not name a day. Narrow markets have a way of grinding higher far longer than the divergence "should" allow, right up until they don't.

Breadth is one of the more honest tools in this book precisely because it measures something real — participation — rather than pretending to forecast. But it has firm limits.

It cannot time anything. A breadth divergence is a description of the present, not a schedule for the future. Divergences can last weeks or months, and some are resolved not by price falling but by breadth quietly recovering as more stocks join in. Anyone who tells you a divergence means a crash "within days" has added a precision the tool does not contain.

It can be legitimately narrow. Sometimes a few genuinely dominant companies deserve to carry an index — a real technology or earnings shift concentrated in a handful of giants. Narrow is a warning, not a verdict of fraud. The market can be right to reward the few and abandon the many; breadth flags the concentration, it does not tell you whether the concentration is justified.

It says nothing about which stocks to own. Breadth is a weather report for the whole market, not a stock picker. A healthy breadth backdrop still contains falling stocks, and a poor one still contains rising ones. And it says nothing at all about any company's accounts, cash flows or value — it is a map of the crowd, not a reading of any business.

And there is the familiar backtest trap. It is easy to line up "the A/D line diverged before the last three big tops" and feel you have found a rule. But the divergences that led nowhere are missing from that tidy list, and three matches are not a law. A signal remembered only through its hits, with its misses forgotten, will look far more reliable than it is.

Turning a soft warning into a hard date. The single most common error. "Breadth diverged, therefore crash next week" converts a genuine caution flag into a false prediction, and when the crash does not arrive on schedule, people conclude breadth is useless — throwing away a good context tool because it was misused as a timing tool.

Watching the wrong universe. The advance/decline line for a narrow, large-cap index is far less informative than one computed across a broad universe of stocks. If you want to know whether the whole market is participating, you have to count the whole market, not just the fifty biggest names. In India, the broader all-market breadth often turns down well before the top-heavy headline index does.

Confusing weight with count. Breadth counts stocks, one vote each — a giant and a tiddler count the same. The index weights by size. That difference is the entire point: it is why breadth can diverge from the index. Someone who "corrects" the count by re-weighting it back toward the giants has simply rebuilt the index and thrown breadth away.

Assuming broad means safe. A broad, healthy backdrop lowers the odds of a fragile top, but it is not armour. A genuine shock can knock over even a wide, well-supported market; good breadth improves your odds, it does not suspend the possibility of a fall.