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2013 Arbitron Population Updates

November 1, 2012

Each year, effective with the October PPM and Fall diary books, updated population numbers are incorporated into Arbitron’s radio audience estimates. Changes within a station’s key demographic can significantly impact its ratings, even if panelists’ listening hasn’t changed at all.

Arbitron receives its population data from a third-party vendor, Nielsen Claritas. The 2012 population estimates, last used in the September 2012 PPM and Summer 2012 diary surveys, were based on Census 2010 data that was projected to 2012. Beginning with the October 2012 PPM and Fall 2012 diary surveys, the population estimates are based on Census 2010 data projected to 2013.

Arbitron uses population estimates in order to model their sample as similarly to the population as possible – demographically, ethnically, geographically, and socioeconomically. For example, if 20% of a market’s population are Hispanic, Arbitron will attempt to compose its sample of 20% Hispanic panelists.

Ideally, each meter represents the same number of people in the metro as every other meter. However, when Arbitron over- or under-samples a particular group, they employ weighting. This means that a meter in an under-sampled group will represent more people than a meter in an over-sampled group. In my example from the previous paragraph, if the market is 20% Hispanic but the sample is only 10% Hispanic, Arbitron would double the “value” of those meters so that reported radio estimates reflect listening from 20% Hispanics.

Due to weighting, stations whose audience is under-sampled may notice greater fluctuations in their data compared to stations whose audience is not under-sampled. If a panelist with abnormal listening habits is from an under-sampled group, their meter or diary value will be more heavily weighted. This means that the abnormal listening habits are magnified. That’s why it’s so crucial to take a look at the population updates each year to see if there were any major changes in your station’s key demographics.

If you’re in a PPM market, your October book just released this week. If you’re in a diary market, your Fall Arbitrends data begins releasing this month, with the Fall book out in January. If you have any questions about how these population changes affect you, give us a shout.

-Anne Doyle, Programming Research Consultant

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