Breadth Thrusts

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.

Several variants live under the same umbrella. Wayne Whaley catalogued thrusts in advance/decline and up-volume ratios over roughly week-long windows, and Walter Deemer's breakaway momentum requires cumulative 10-day advances to be at least 1.97 times cumulative 10-day declines. 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.

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/down volume and the McClellan Oscillator, 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.