Double Jeopardy Law

The pattern, identified by William McPhee in 1963 and extended by Andrew Ehrenberg, that small brands have fewer buyers who are also slightly less loyal.

By Brandon MinaCEO, BrandPilot AIUpdated November 2026

Short answer

The Double Jeopardy Law is the pattern that small brands have fewer buyers, and those buyers are also slightly less loyal. It was identified by William McPhee in 1963 and extended to marketing by Andrew Ehrenberg. It implies that brands grow mainly by gaining more buyers rather than by increasing loyalty alone.