By Jennifer Armstrong
May 19, 2009 at 09:16 PM EDT

Fox’s public criticisms of the Nielsen ratings service have become the latest knock to the age-old system of counting how many people watch primetime shows — you know, the thing that determines whether series live or die. The criticism itself is boringly technical: The ratings giant recently did a study to determine why some Nielsen families were screwing up the way they record their viewing choices, so much so that the readings could be off by about 8 percent. In the ratings biz, especially these days as viewer totals shrink thanks to cable and DVRs, 8 percent can mean a lot. As in millions of dollars, which is why Fox is upset. (Nielsen responded that the study was meant just to fix internal problems, not to determine an actual margin of error.)Fox Networks Group chairman and CEO Tony Vinciquerra specifically questioned the numbers for TV’s biggest hit (and his net’s cash cow), American Idol: “It’s been a hugely successful season, yet the ratings are down 11 percent,”he said. “There are significant, double-digit gains in (the show’s)votes, and there’s been a huge response. We believe the show is doingbetter than we see in the ratings.”

It’s the latest in a series of problems Nielsen: ABC President Steve McPherson also has questioned their accuracy recently, Miami-based station owner Sunbeam filed a suit claiming the company is a monopoly, and primetime ratings were delayed for days earlier this month because of a computer glitch. TiVo, meanwhile, has been inching closer to becoming an alternative to Nielsen.

But for all of its problems, Nielsen will likely live on for a while. First of all, the panicking networks can’t blame all their problems on Nielsen — numbers are plummeting because people are watching TV differently. Even my parents have a DVR, which means that trend has reached critical mass; I also know huge TV fans who don’t actually own TVs. (They watch everything online.) And BTW, cable hits and broadcast hits are approaching parity in terms of numbers, all hovering in the 6- to 12-million range. If people are voting more on American Idol, it’s probably just because more folks have figured out how to text and call in multiple votes, and a higher percentage of viewers are voting. (Again, I base this on unscientific Mom Data: If my mom can text it up for Adam Lambert, anyone can.)

What do you think, PopWatchers? Do the Nielsen numbers you read about seem accurate? Should TV networks find a better way to measure viewership?

addCredit(“Frank Micelotta/Fox”)