• by Erik Sass  @eriksass1, July 21, 2010

Radio presents a textbook case of a mature medium, judging by the first batch of year-over-year results from Nielsen's new radio ratings service, which found that the radio audience remained remarkably stable from 2009-2010.

The data from Nielsen seem to corroborate separate findings released by its competitor Arbitron, also indicating that radio attracts a large, consistent audience.

Overall, Nielsen found that radio reached 91.4% of Americans ages 12+ this year, up slightly from 90.2% last year. Nielsen also found that cell phone-only households (without landlines) also tend to be heavier radio listeners than the population at large, with 94.3% reach.

This finding appears to contradict conventional wisdom that CPO households -- which skew younger, on average, than the general population -- would show lower rates of radio listening.

On a related note, Nielsen found that the listening habits of adults ages 18-34 conform with other cohorts in the 12+ age group, reaching 92.8% of this group on a weekly basis. Weekly listening by African-American and Hispanics also conforms to the broader average: 91.2% and 92.9% for these ethnic audiences, respectively.

The Nielsen data is drawn from panels of 115,672 consumers across 51 midsized U.S. markets, representing a total audience of 14 million, Last year, Nielsen introduced a new radio ratings service using diaries and stickers to compete with Arbitron's existing diary service.

Nielsen claims its service delivers more accurate audience representation than Arbitron, thanks to an address-based (rather than phone-based) sampling methodology, which takes into account the growing number of cell phone-only households.

Setting aside their competitive rivalry, the Nielsen and Arbitron data generally seem to be in agreement about the stability of radio audiences over time.

In June, Arbitron released the results of its most recent RADAR measurement, showing that 220 million people ages 12+ listened to the 7,200 radio stations in the RADAR affiliate network. That's up slightly from 213 million in 2009. Arbitron found that radio reaches 93.1 percent of Americans 12+ each week, closely echoing Nielsen's findings.