gerald goodhardt born 1930 is a marketing scientistapart from being the chairman of the board at the ehrenbergbass institute for marketing science professor gerald goodhardt is emeritus professor city university visiting professor kingston university and also a visiting research associate south bank university formerly sir john e cohen professor of consumer studies and dean of the city university business school gerald has spent 20 years in industry and commerce prior to 20 years as an academic he has served as chairman of the market research society gold medalist in 1969 and 1996 and as hon secretary of the royal statistical society gerald was also founding president of the market research benevolent association published extensively in marketing and statistical journals mainly in quantitative aspects of consumer behaviour and the audiences use of broadcast media professor goodhardt began his career working as a statistician for attwood panels and later aske research with andrew ehrenberg from 198195 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 finally published in 1984 the nbddirichlet model of brand choice successfully modeled the repeated category and brand purchases within a wide variety of markets the dirichlet as it became known accounts for a number of empirical generalisations including double jeopardy the duplication of purchase law and natural monopoly it has been shown to hold over different product categories countries time and for both subscription and repertoire repeatpurchase markets it has been described as one of the most famous empirical generalisations in marketing independently and at about the same time schmittlein bemmaor and morrison published the same model in marketing science and showed a variety of its statistical properties in particular when it reduces to the simple nbd model they labelled the univariate model as beta binomialnegative binomial distribution bbnbd the model has since been extensively applied both by academics and marketing research consultancy firms