Double Jeopardy

What it is

The pattern was first described by the sociologist William McPhee in 1963, in awareness and liking scores, and Andrew Ehrenberg extended it to what people actually buy. The formalisation usually cited is Ehrenberg, Gerald Goodhardt and Patrick Barwise's "Double jeopardy revisited", in the Journal of Marketing in 1990.

Byron Sharp's How Brands Grow puts numbers on it. In United Kingdom washing powder in 2005, Persil held 22 per cent of the market and was bought by 41 per cent of households in a year, at 3.9 purchases per buyer. Surf held 8 per cent, reached 17 per cent of households, and its buyers bought it 3.4 times. Persil's lead was almost entirely in reach. The loyalty gap was half a purchase a year.

A 2017 review led by Charles Graham, in the Australasian Marketing Journal, drew on 179 peer-reviewed publications and 32 further replications, and reported finding no boundary condition for the pattern.

In effect

If loyalty mostly follows size, a small brand trying to win by deepening loyalty is pushing against the arithmetic. Growth, on this account, comes mainly from reaching more buyers.

For a shopper, it changes how your own loyalty reads. Feeling loyal to a big brand is real in the sense that you buy it often, but it is largely what buying a widely available, frequently noticed brand looks like. A loyalty scheme run by a large brand mostly rewards buying that its size had already produced.

What it does not say

It does not say loyalty is fake, or that service quality is irrelevant. Research linking customer satisfaction to company performance finds a real association, modest and conditional; the double jeopardy tradition disputes the causal reading, not the link.

It does not hold everywhere without exception. Niche brands can show more loyalty than their size predicts, change-of-pace brands less, and Sharp's own banking table runs mildly against the pattern.

It does not rest on independent replication alone. Much of the evidence comes from one research tradition, which has found it many times; that is a dependency worth knowing about, not a reason to doubt the pattern.

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