What's a better measurement of radio listenership: numbers that show all levels of exposure to a radio station, or numbers that show how many people are actually paying attention to what they're hearing?

That question was debated between executives from Spanish-language radio and Arbitron at the "People Meter: Friend or Foe?" panel at the Billboard Latin Music Conference today (Monday) at the Seminole Hard Rock Hotel in Hollywood, Fla.

The Personal People Meter (PPM) is a pager-like device that detects what radio stations people who are selected to wear the devices are exposed to. Arbitron believes that the PPM system, which is replacing self-reported paper diaries as a measurement of radio ratings, will provide a more frequent and accurate read of what programs, music and commercials listeners are exposed to-and allow radio stations to compete more effectively for advertising dollars.

But "not all of what you are exposed to is what you listen to," said Ceril Shagrin, Univision Communications' executive VP of corporate research. "Very frequently, Hispanics are exposed to English radio. They go into a store, they are driving next to a car...the meter picks it up. The reverse is not true. We're looking at something that is going to impact Spanish radio more than English radio."

Shagrin also expressed concerns over sample size, and the ability for Arbitron to accurately represent Hispanic listeners, whose listening habits vary widely according to geographic location, country of origin, and whether they are Spanish- or English-dominant.

Stacie de Armas, Arbitron's director of multicultural services, said even passive or involuntary exposure to a radio station should count toward its ratings. Also, she said compliance with the system within the sample has been good, according to Arbitron's studies.

"Based on our targets, [in terms of] how many people are actually complying and carrying [the device], regardless of race and ethnicity-performance is pretty much in line," she said.

Ed Cohen, Arbitron's VP of research policy and communication, said long periods of exposure to a station -- rather than incidental -- would ultimately be counted more and make a bigger difference in ratings anyway.

Frank Flores, VP and marketing manager for SBS New York, said PPM-based results had been "devastating" to two of his stations, WSKQ and WPAT. In February, WSKQ and WPAT respectively went from being ranked No. 2 and No. 8 in the market to No. 11 and No. 20.

"It is going to affect our revenue," said Flores. Predicting that radio stations would flip to more widely-exposed English-language formats to keep up with the new ratings system, Flores said, "there are going to be some [Spanish-language] radio stations that are not going to be able to survive."