How Do TV Sweeps Periods Work?

Television’s February sweeps period started Thursday and runs through March 2, so brace yourself for a slew of guest stars, wedding episodes, and other attention-grabbers. We all know that TV networks try to spike their ratings during sweeps, but how exactly does the system work? Why do networks care about these particular weeks in the first place? Let’s take a look at some sweeps questions.

© Bettmann/CORBIS

When did sweeps begin?

The idea of sweeps dates back to 1954. That year, ratings research juggernaut Nielsen began sending a sample of households around the country little diaries in which the family would record everything it watched on TV for a seven-day period. These diaries were then returned to Nielsen and used to estimate the size of shows’ audiences. Over time, the sweeps period got longer, and even though we still hear talk of “sweeps week,” the modern sweeps period actually lasts four weeks.

How did we end up with this system?

Blame our crummy collective handwriting.

When Nielsen began sending out the viewing diaries in 1954, it was apparent that taking the time to read and collate all of the data from thousands of handwritten diaries was a pretty epic task. To cut down on the workload, Nielsen decided it would only send out diaries for four-week periods four times a year. Viewers would get the diaries in February, May, July, and November, and the data collected in each survey could be used for the next three months.

Where did the name “sweeps” come from, then?

The name “sweeps” is another artifact of Nielsen’s early methodology. Collecting all of those diaries and recording the data was thorny task, so to simplify the process the company collected the seven-day diaries by region. Nielsen collected the Northeast’s diaries first and then “swept” across the country until it had the logs of West Coast viewers.

Do sweeps really “set the advertising rates” for the next quarter?

Yes and no. National ads make up the majority of networks’ advertising revenues; a typical half-hour primetime show will feature six minutes of national ads and just two minutes of local ads. Sweeps don’t affect the rates for national ads, which are set using year-round national data.

Sweeps do affect the rates for the two minutes of local ads, though. The month-long bonanza of stunt casting and very special episodes determines how much local advertisers will be shelling out to air their ads for the following three months. This system gives networks a huge financial incentive to cram every ratings-grabbing ploy they can into any sweeps period.

Is it just me, or does this system make zero sense?

It’s not just you. Back in the days when all of the viewing diaries were handwritten, the logistical hurdles of collecting the data made the sweeps system seem reasonable. Now that the process could be computerized, it makes much less sense. The system is somewhat akin to not eating for a week before weighing yourself then claiming the scale’s readout is your “real” weight.

Local advertisers loathe the sweeps system because it artificially inflates audience numbers, which in turn inflates the ad rates they have to pay. Networks and commission-based ad agencies love sweeps for just this reason, though. Since the local advertisers are mostly relatively small ad buyers in the grand scheme of things, they don’t have much leverage, so the sweeps system can continue to flourish.

Do people really still fill out paper diaries?

Yes. A 2004 piece by Sean Rocha in Slate estimated that Nielsen was still leafing through 1.6 million diaries each year. Nielsen has rolled out an automated alternative called the Local People Meter that can register audience information easily and more reliably. According to Nielsen’s website, the Local People Meters are already in place in the country’s largest media markets, and in 2007 the company announced plans to roll the LPM technology into 56 of the top 63 media markets. Theoretically, these meters could spell curtains for sweeps because they could easily and accurately estimate year-round audience sizes without the need for arbitrary sample periods like sweeps.