Radio broadcasters, preparing to descend on Philadelphia for the National Association of Broadcasters annual convention, may find the ratings from Arbitron’s portable people meter trial in Houston a tough pill to swallow.

Overall, average quarter hour ratings are down by 20 percent compared to diary measurement, with morning drive, radio’s biggest revenue-generating daypart, taking the biggest hit, down by more than 35 percent. Midday ratings were also lower under the PPM, down 21.9 percent. Other dayparts were down on average by 12 percent. [Media Week]