ABC:
9pm - Dancing With The Stars - 20.97m (4.5)
* Season finale
* Up 15% from 2010 spring finale (its lowest ever)
* Up 29% from last week
* Final half hour - 22.59m (5.0)
FOX:
8pm - American Idol - 19.96m (6.2)
* Down 7% from last years final numbers
* Down 16% from last weeks finals
* Second lowest rated in season performance show ever
* Likely to end up similar to last year in total viewers
9pm - Glee - 12.10m (4.6)
* Season finale
* Highest rating since March
* Retained 74% of lead-in and held throughout the hour (first half - 4.8, second half - 4.5)
* Up 28% from last week
NBC:
8pm - The Biggest Loser - 8.08m (3.1)
* Season finale
* Up 11% from last week
* Down 21% from last spring
* Lowest ever finale episode
10pm - The Voice - 8.55m (3.8)
* Down 16% from last week
* Has lost 1.9 points in 3 weeks (33%)
http://tvbythenumbers.zap2it.com/201...e-voice/93836/
So, that didn't turn out as I expected!

So what happened?
Firstly, for Idol. One factor is that it aired for just one hour at 8pm - the first time this season it hasn't run at least 90 minutes. Aside from the fact that 8pm rates worse than 9pm, these shows build over their runtime anyway. But even compared to the 8pm hour (6.7) last week, it was down quite a bit. Perhaps the change of night caught people out. A Tuesday semi-final earlier this season didn't see any notable change so I can see why FOX wouldn't have expected it to make a difference now.
NOTE: When I say second lowest "in-season", it means September-May. Season 1 had lower episodes but they all aired in the summer. The lowest is a top 5 show last season which had a 6.2 and 17.5m viewers. In finals, last nights show will likely eclipse that number.
Great numbers for DWTS. ABC already have a
press release out which notes that it's the first show ever to top a Tuesday finale of American Idol.
The Voice is more of a puzzle. You'd think that if it just lost viewers to DWTS, it would have seen a proportionately greater fall in total viewers than A18-49? But as it happens, it was the other way around with total viewers down just 13%. Furthermore, it had a stronger lead-in than last week and only built slightly on the 3.6 for the final half hour of TBL whereas it has tended to grow significantly.
Next week, the lead-in is America's Got Talent. The season 5 premiere averaged a 3.6 rating and finished up with a 4.0 (or a 4.1, can't remember exactly) in the final half hour. The following week, The Voice shifts to 2 hour shows from 9-11pm with AGT airing 8-9pm.