We have observed that competitive repeat purchase markets are polarised into two radically different structures. The first and best known we call repertoire markets; these have few solely loyal buyers as most buyers allocate their category requirements across several brands in a steady fashion. The other we call subscription markets; these have many solely loyal buyers as most buyers allocate category requirements entirely to one brand. This is an empirical difference rather than a theoretical distinction, and surprisingly there appear to be no markets which occupy the middle ground between these two extremes. The repertoire-subscription distinction turns out to be an important boundary condition for some well-established generalisations about repeat purchase behavior. Despite this, the NBD-Dirichlet model of purchase incidence and brand choice fits both types of markets, and the differences in loyalty are adequately captured by the Dirichlet's switching parameter, S. This represents an important extension of the generalisability of the Dirichlet, allowing the insights gained from repertoire market analysis to be applied to customer churn analysis in subscription markets.

The prevalence of faulty citations impedes the growth of scientific knowledge. Faulty citations include omissions of relevant papers, incorrect references, and quotation errors that misreport findings. We discuss key studies in these areas. We then examine citations to “Estimating nonresponse bias in mail surveys,” one of the most frequently cited papers from the Journal of Marketing Research, to illustrate these issues. This paper is especially useful in testing for quotation errors because it provides specific operational recommendations on adjusting for nonresponse bias; therefore, it allows us to determine whether the citing papers properly used the findings. By any number of measures, those doing survey research fail to cite this paper and, presumably, make inadequate adjustments for nonresponse bias. Furthermore, even when the paper was cited, 49 of the 50 studies that we examined reported its findings improperly. The inappropriate use of statistical-significance testing led researchers to conclude that nonresponse bias was not present in 76 percent of the studies in our sample. Only one of the studies in the sample made any adjustment for it. Judging from the original paper, we estimate that the study researchers should have predicted nonresponse bias and adjusted for 148 variables. In this case, the faulty citations seem to have arisen either because the authors did not read the original paper or because they did not fully understand its implications. To address the problem of omissions, we recommend that journals include a section on their websites to list all relevant papers that have been overlooked and show how the omitted paper relates to the published paper. In general, authors should routinely verify the accuracy of their sources by reading the cited papers. For substantive findings, they should attempt to contact the authors for confirmation or clarification of the results and methods. This would also provide them with the opportunity to enquire about other relevant references. Journal editors should require that authors sign statements that they have read the cited papers and, when appropriate, have attempted to verify the citations.