[1] Goodhardt began his career working as a statistician for Attwood Panels, and later Aske Research with Andrew Ehrenberg.
From 1981-95 he was Sir John E Cohen Professor of Consumer Studies at The City University Business School.
In the early 1980s, with Andrew Ehrenberg and Chris Chatfield, he extended the NBD model to account for brand choices.
[2] 'The Dirichlet', as it became known, accounts for a number of empirical generalisations, including double jeopardy, the duplication of purchase law, and natural monopoly.
[3] It has been shown to hold over different product categories, countries, time, and for both subscription and repertoire repeat-purchase markets.