How rare is a Zweig Breadth Thrust?

Genuinely rare: published counts typically find only a handful per decade on NYSE data, though exact tallies vary with the data vendor and how the advance/decline universe is defined. That scarcity is the point of the signal, but it also means the historical sample is small, so any track record attached to it carries wide statistical uncertainty.

Does a breadth thrust guarantee a new bull market?

No. Thrusts have a strong historical association with the early stages of durable advances, but the sample is small, some signals have fired inside bear-market rallies, and market structure changes across decades. Most practitioners treat a thrust as a meaningful shift in evidence that still needs price confirmation and normal risk management.

What exactly triggers a Zweig Breadth Thrust?

Take advances divided by advances plus declines each day, smooth with a 10-day exponential moving average, and require the average to move from below 0.40 to above 0.615 within ten trading sessions. Both legs matter: the washout below 0.40 and the speed of the recovery. A slow climb through the same levels does not qualify.

What is Deemer's breakaway momentum?

Walter Deemer's version, developed in the 1970s, sums NYSE advances and declines over ten trading days and signals when cumulative advances reach at least 1.97 times cumulative declines. It uses raw totals rather than a smoothed ratio, so it and the Zweig rule can fire at different times off the same underlying data.

Why do breadth thrust dates differ between sources?

Because the inputs differ. All-issues NYSE data includes funds and preferred and interest-rate-sensitive securities, while common-stock-only series exclude them; vendors also differ in how they seed the exponential average and handle historical revisions. Marginal signals can appear in one dataset and not another, so serious users state which universe they computed on.

Is there a bearish equivalent of a breadth thrust?

The classic definitions are one-sided, built to catch upside initiation after washouts, and the absence of a thrust is not a sell signal. Downside analogues exist in practice, such as studies of overwhelming down days, but they are separate tools with their own evidence rather than a mirror image of the Zweig rule.

Concept

Breadth Thrusts

Breadth Thrusts, also known as Zweig, Whaley, are Breadth, Sentiment & External Data concepts.

What are Breadth Thrusts?

Breadth thrusts are rare, high-velocity swings in market breadth from washed-out to overwhelmingly positive, read as evidence that buying has broadened enough to start a durable advance. The classic definition is Martin Zweig's: the 10-day exponential moving average of advances divided by advances plus declines rises from below 0.40 to above 0.615 within ten trading sessions. The logic is that ordinary rallies recruit buyers gradually, while a thrust compresses that recruitment into days, something that historically has tended to happen near major lows rather than inside routine ranges.

Zweig popularized the rule in the 1980s, the era of his book Winning on Wall Street, after studying how the strongest advances began. Several variants live under the same umbrella: Wayne Whaley, in a Charles H. Dow Award-winning study of thrust measures, catalogued thrusts in advance/decline and up-volume ratios over roughly week-long windows, and Walter Deemer's breakaway momentum, a concept he developed in the 1970s, requires cumulative 10-day advances to be at least 1.97 times cumulative 10-day declines.

Computation details matter more than they look. The inputs are daily counts of advancing and declining issues, so the choice of universe changes history: all NYSE issues include funds and interest-rate-sensitive securities, while common-stock-only versions behave differently, and some signals appear in one dataset but not the other. That is one reason published thrust records differ across vendors.

All versions share the same caveats: signals are scarce, the historical sample is small, and a completed thrust shifts the weight of evidence rather than guaranteeing a new bull market. The underlying idea is initiation. A durable advance needs broad participation, and a thrust is the sharpest measurable form of it, the moment a market goes from most stocks falling to nearly everything rising at once.

How to identify a breadth thrust

Using the Zweig version as the template:

1Compute the daily breadth ratio, advances divided by advances plus declines, for your chosen universe, classically NYSE issues.
2Smooth it with a 10-day exponential moving average and mark the two thresholds, 0.40 and 0.615.
3Arm the signal when the average closes below 0.40, the washed-out condition.
4Fire it only if the average then closes above 0.615 within ten trading sessions; slower recoveries do not qualify.
5Cross-check the same window against an independent definition, such as Deemer's 1.97 ratio of 10-day advances to declines or Whaley's up-volume thrusts, since overlapping signals from separate definitions strengthen the case.

How traders use it

As regime confirmation after a decline: a completed thrust argues for treating subsequent pullbacks as buyable rather than as rallies to fade, a bias adjustment rather than an entry trigger.
Cross-checked against other internals, such as up-volume ratios, the McClellan Oscillator, the intraday TICK Index, and the percentage of stocks above their 20/50/200-day averages, to distinguish broad initiation from a narrow short squeeze.
As a deployment filter: some position traders scale exposure up only when participation measures like advance/decline internals confirm the thrust, rather than acting on index price alone.
Read against the volatility backdrop: practitioners give more weight to thrusts that arrive as the VIX retreats from panic levels, the classic bottoming sequence, and less to those printed while volatility is still climbing.
As a starting gun for leadership work: after a thrust, traders turn to relative strength comparisons and ratio charts to find the groups driving the new advance, since early leadership frequently sets the tone for the move.

Breadth thrusts vs. related breadth measures

Advance/decline Internals: A/D internals are the daily raw material, breadth readings available every session. A breadth thrust is a rare event defined on top of them, a specific velocity pattern in those internals rather than a different dataset.

% Stocks Above 20/50/200-day MA: Percent-above measures show the level of participation at a point in time; a thrust measures its rate of change from washout to near-unanimity. A market can sit at high participation for months without ever printing a thrust.

TICK Index: The TICK counts NYSE stocks upticking minus downticking moment to moment, breadth at intraday speed. Thrust signals live on daily data over one-to-two-week windows; the TICK helps time entries, not define regimes.

Concept family

Breadth, Sentiment & External Data

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