Arbitron may have handed its critics another argument for why the portable people meter service is not ready for prime time. On Tuesday (May 26), the radio ratings company told its subscribers that the last four months of monthly ratings based on the PPM service would need to be reissued.

The Big Apple-sized snafu was due to an incorrectly entered population estimate. Revised New York estimates for the four months, Holiday 2008 (mid-December to early January) to March 2008 will be published June 8.

In its monthly conference call with PPM customers, Arbitron tried to reassure the business it was taking appropriate measures to prevent future errors. "Please note that we are taking additional quality-control measures for future reports," Arbitron said in its client notice. "These measures include the replacement of manual processes that rely on clerical data entry with automated processes where possible."

No doubt Arbitron's PPM customers will be counting on more careful procedures for the new electronic ratings service.

The Arbitron PPM methodology has faced ongoing criticism from a number of ethnic broadcasters that claim the PPM undercounts minority audiences. Univision Communications recently said in its quarterly call that it would not use PPM ratings to sell commercial time on its stations in unaccredited PPM markets. The Spanish-language broadcaster has also elected not to encode its signals in Miami and other soon-to-be commercialized PPM markets.

While Media Rating Council accreditation could quell PPM's critics, the double check mark has been hard to come by for Arbitron. Of Arbitron's 15 PPM markets, only Houston and Riverside-San Bernardino, Calif. have been accredited.