THE WAY WE WATCH.(TV sweeps system)

In the next few weeks, Trista the bachelorette will finally choose her man, Joe Millionaire will come clean, Demi Moore will play an ex-babysitter on "Will & Grace," and "Dateline NBC" will devote a full, solemn hour to the medical marvel that is Michael Jackson's face. And to what do TV viewers owe such munificence? To the advertisers' hunger for information about who watches what, a hunger that manifests itself, four times a year, in a monthlong viewer-data harvest known as "sweeps."

When advertisers are deciding which shows to buy time on, they want to know not just how many people are watching but what kinds of people, too. So Nielsen Media Research has wired five thousand American homes with electronic "people meters," which enable it to collect national ratings and demographic information on behalf of the major networks. The networks, in turn, use that information to sell national advertising.

Not all the ads you see are national, though. A sizable percentage are tailored to local markets--think Fudgie the Whale or Wiz Bucks, in New York--and local advertisers also need demographic information. The problem is that Nielsen doesn't have people meters in each of America's two hundred and ten television markets. So those people meters don't tell local advertisers what local folks are watching.

This is where sweeps come in. The sweeps system, which originated in radio, has been around for almost fifty years, and it shows. Every February, May, July, and November, Nielsen sends out 2.5 million paper "diaries" to randomly selected people in almost every TV market in the country and asks them to record, for a week, what programs they watch. The networks' local stations--the affiliates--and local advertisers then use the information from those diaries to negotiate ad ratesfor the months ahead. Each year, sweeps determine how more than twenty billion dollars in ad money gets spent.

There are three important things to know about sweeps. The first is that they are deeply flawed, and of little use, in the end, to the networks, the advertisers, and the viewers. The second is that everyone in television knows this. The third is that no one has done anything about it. "They're just an unwelcome phenomenon we have to deal with every three months," David Poltrack, the head of research at CBS, says. "I don't know anyone who thinks they're good for the business. But, for now, we're stuck with them."

What's wrong with them? To begin with, they force the networks to rely on "stunt" programming--to pack their schedules with outrageous specials, celebrity appearances, and expensive movies. The more juicy stuff the networks pack into sweeps months, the less they can afford to put on during the rest of the year.

Advertisers, for their part, wind up paying for ratings that often reflect only this stunt programming. "Because the networks and the ...