Station PPM Ratings and In-Tabs

Harker Research has long observed that as the number of Arbitron diaries in a cell increased, the ratings of stations targeting that cell rose. And conversely, if Arbitron fell short in a demo, some stations would suffer much greater loses than others. Now Randy Kabrich has documented a similar phenomenon with PPM.

As reported in today's RBR.com here, the ratings of both KMJQ and KBXX rose in virtual lock-step with an increase of Houston's Black in-tab. It stands to reason that as additional African-Americans are added to the panel, that stations targeting African-Americans would benefit, but according to Arbitron, this should not happen. Arbitron uses a complex weighting process that balances each day's PPM data according to age, sex, race, and county of residence so that the day's panel represents the market's characteristics. Theoretically, as more Black PPMs are added to the sample, the weight of each Black PPM goes down. As a result, there should be no relationship between station performance and panel composition. Look at Mr. Kabrich's data and you be the judge.