McGinley Dynamic

What is the McGinley Dynamic?

The McGinley Dynamic is an adaptive smoothing line developed by market technician John R. McGinley in the 1990s to address a standing complaint about moving averages: a fixed length is always tuned for one market speed, so the line lags badly in fast markets and hugs too closely in slow ones. Each bar, the McGinley Dynamic moves toward price by the distance between price and the line, divided by N times the fourth power of the price-to-line ratio. That ratio term is the whole mechanism: when price falls below the line, the divisor shrinks and the line chases price down quickly; when price stretches above, the divisor grows and the line advances more reluctantly.

The asymmetry is deliberate. McGinley built the formula around the observation that markets fall faster than they rise, so the line is designed not to get stranded far above a falling market while staying smooth through advances. N is a smoothing factor rather than a literal bar count; McGinley's own guidance was to use roughly 60% of the EMA or SMA length you would otherwise choose. It remains a lagging, price-following line: it reduces separation and whipsaw, it does not eliminate them.

How traders use it

• As a trend baseline: slope and price's side of the line define bias, the same role an EMA plays, with speed that self-adjusts instead of being fixed by the length setting.
• As the smoothing engine inside other constructs: substituting the McGinley Dynamic for conventional averages in crossover systems or MACD-style spreads to cut whipsaw from mis-fit lengths.
• As one of several adaptive averages, alongside KAMA and VIDYA, compared when a strategy's fixed-length average keeps being wrong-footed by regime changes.