Byron Sharp

Byron Sharp

Marketing scientist at the Ehrenberg-Bass Institute and author of How Brands Grow (2010), the book that carried decades of buying-behaviour research to a general marketing audience. On this site he is the source for double jeopardy, buyer moderation and the sixty twenty rule as they appear in his book.

Who they are

Sharp's book argues that brands grow mainly by reaching more buyers rather than by deepening the loyalty of existing ones, and supports the argument with tables of household panel data across many categories and countries. It credits the patterns it uses to earlier researchers, Andrew Ehrenberg above all, and states several of its own limits in footnotes.

Roughly a third of the book's sources come from his own institute or its lineage, which is what one would expect from a single large research programme and is worth knowing when weighing it.

Key papers

Sharp, B. (2010). How Brands Grow: What Marketers Don't Know. Oxford University Press.

Sharp, B., Romaniuk, J., & Graham, C. (2019). "Marketing's 60/20 Pareto law." SSRN working paper. doi:10.2139/ssrn.3498097.

Key ideas

Loyalty mostly follows brand size. See Double Jeopardy.

The heaviest fifth of buyers supply far less than 80 per cent of sales. See The Sixty Twenty Rule.

Heavy buyers drift back towards average. See Buyer Moderation.

Sources

  1. Sharp, B. (2010). How Brands Grow. Oxford University Press. Read in full by this publication, 8 October 2026.