NEW YORK (AP) — The Nielsen company on Friday admitted to errors dating back to March in its measurement of television viewing, statistics that serve as the foundation for billions of dollars in advertising spending for the entire broadcast industry.

The company blamed a software glitch for errors that, industry officials said, mistakenly credited ABC for viewing that was in reality spread across all of the broadcast networks. Nielsen described the errors as minuscule, but the extent will become better known next week when the company issues corrected ratings for the first week of the television season.