McClellan Oscillator

The McClellan Oscillator was developed by Sherman and Marian McClellan in 1969 and published in their book Patterns for Profit. It applies the MACD moving average divergence methodology — familiar from price chart analysis — to market breadth data, specifically the daily net advancing issues on the New York Stock Exchange (the number of stocks advancing minus the number declining).

The construction begins with the daily net advance-decline figure. A 19-day exponential moving average (EMA) of this figure captures short-term breadth momentum, while a 39-day EMA captures intermediate-term breadth momentum. The McClellan Oscillator is the difference between these two values: 19-day EMA minus 39-day EMA. Like a standard MACD, it oscillates above and below zero. When it is positive, short-term breadth momentum is stronger than intermediate-term breadth, historically a constructive sign. When it is negative, short-term breadth has deteriorated relative to the medium-term trend.

Historically, analysts have used the McClellan Oscillator in several ways. Extreme positive readings — traditionally above +100 — were sometimes observed in the early phases of strong rallies or following oversold market conditions, reflecting the burst of broad participation that characterizes genuine recoveries. Extreme negative readings below -100 were historically associated with market conditions where selling pressure was very broadly distributed, sometimes preceding near-term market stabilization as oversold conditions became exhausted.

Divergences between the oscillator and price indices have been particularly noteworthy in historical analysis. When major indices like the S&P 500 were reaching new highs while the McClellan Oscillator was posting lower highs — failing to confirm the price advance with improving breadth momentum — this negative divergence historically suggested that the rally was becoming increasingly concentrated and potentially vulnerable.

The oscillator is also a key component in confirming the conditions required for the Hindenburg Omen: one of the traditional criteria for a valid Hindenburg Omen signal is that the McClellan Oscillator must be negative on the day the high-low breadth divergence is observed.

As with all breadth indicators, the McClellan Oscillator requires context for meaningful interpretation. Its readings are affected by the total number of NYSE-listed issues, structural changes in the market's composition over time, and broader macro regimes. Analysts typically review it alongside the McClellan Summation Index (its cumulative version), advance-decline line data, and price trend analysis to build a comprehensive picture of market breadth conditions. Its value lies not in any single reading but in the pattern of readings over time — whether momentum is improving, deteriorating, confirming price trends, or diverging from them.