I think sweeps periods are becoming less and less important. The advertisers are getting too hip to the tricks the networks use to boost ratings. That's what I read somewhere, anyway.
No, they're just creeping backwards - "May" sweeps actually extends a week or two back into April this year. I'm not sure why, other than some calendrical oddity I'm not seeing, but it does work to the networks' advantage - a shorter effective season means you don't have to stretch 22 episodes quite as far.
Summer is now becoming a factor for launching shows so May is becoming less important as the "final month" and networks are cutting back on there repeats in March/April to hold onto audiences making May sweeps less of an issue.
Some of the new Fox Summer shows launching in June look interesting
May sweeps is still the same four weeks it has always been (this year, Apr. 29 - May 26), but the networks may well be programming differently than in the past.
Media has its own calendar, a broadcast calendar and months start on the 20 something of the previous month (it varies). NBC scheduled its Friends and Frasier finales "early" for its own strategy purposes. They want to milk it and get attention early and not get caught in the middle of all of the season/series finale stuff mid/late May and lose some of that focus/attention. However, in general, networks are getting more and more away from traditions (in terms of seasons). Regardless, sweeps months are still their means to get ratings for the $ so you will always see event style programs in those months (Nov, Feb, May).
I've been thinking this for years. I can't imagine how advertisers sit back and pay rates for a dud show appearing in something like the 8:30 slot on NBC Thrusdays when the ad rate was set by a sweeps stunt hour long Friends. It just never made sense to me.
Ad rates should be set by indiviudal series, and not a time slot.
Then how do you know what to charge for the first episode of the series?
I imagine that ad rates are figured using a more complex process than "WCSH got a 7 share at 8:30 on the third Thursday of November last year, so an ad on that station for 8:30 on the third Thursday in November costs $20K this year". Besides, there's also make-good promises in the advertising contract, where a network/station has to give free/discounted ads (or, rarely, a rebate) if a series underperforms expected levels.
It doesn't appear much more complex. Regularly some shows are pulled from the air during sweeps, replaced by reruns of more popular shows only for the less popular show to return after sweeps is over. The networks wouldn't do this if it wasn't in some form based on audience levels for a time slot.
Sweeps is obsolete. If they already have a form of discounted ads if a show underperforms in place, than that's what they should stick with. NBC guarantees so much of an audience for "Scrubs", and if they're 5% off their projections, than the client gets so much off of an ad for another airing.
Fox's schedule has been driven by the baseball playoffs and world series for many years. They could premiere their series in September but they would almost immediately be preempted for almost a month losing any initial momentum. Delaying the start helps keep the momentum while also using the sports broadcasts as a platform for promoting the new shows.