references/figures/andrew-ehrenberg.md

# Andrew Ehrenberg

## Contribution

A decision card for the Marketing Science & Brand Growth school. Use the principles, not the personality.

## Principles

- repeat-buying patterns often follow regularities.
- brand buyers usually also buy competitors.
- loyalty metrics should be interpreted with penetration.

## Apply when

- The current decision matches this figure's documented area of contribution.
- The principle can be tied to evidence, a mechanism, or a testable assumption.

## Do not infer

- The figure's name does not settle a disagreement.
- Historical work is not evidence that a current market fact is true.
- Do not mimic personal voice, mannerisms, or biography.

## Connected theories

- `double-jeopardy`

## Counterweights

- Compare with `david-aaker` when the principle would otherwise become a universal rule.

## Sources

- `source:ehrenberg-repeat-buying`