Fast National ratings for Friday, May 18, 2012.
 
Season finales of "Shark Tank" and "Grimm" lifted ABC and NBC into a Friday night split among young viewers, though CBS' repeats still won overall.
 
Meanwhile, The CW got no real boost for finales of "Nikita" and "Supernatural."
 
For the night, ABC and NBC both averaged a 1.3 rating among adults 18-49, tops in the key demographic. CBS and FOX followed with a 0.8 key demo rating, while The CW averaged a 0.5 key demo rating.
 
Overall, though, CBS averaged an estimated 5.44 million viewers and a 3.7 rating/7 share, edging out NBC's 3.4/6 and 5.2 million viewers. ABC was a close third with a 3.1/6 and 4.76 million viewers. There was a big drop to FOX's 2.02 million viewers and a 1.4/3, while The CW averaged a 1.0/2 and 1.52 million viewers.
 
8 p.m. - NBC started primetime in first overall with 5.54 million viewers for the series finale of "Who Do You Think You Are?," which finished second with a 1.0 rating among adults 18-49. "Shark Tank" was second overall with 5.525 million viewers and won the hour with a 1.5 key demo rating. CBS' repeat of "Undercover Boss" averaged 4.26 million viewers and 0.8 key demo, compared to 1.98 million viewers and a 0.8 key demo for FOX's "Kitchen Nightmares" repeat. On The CW, the season finale of "Nikita" was up a hair with 1.465 million viewers and flat with a 0.4 key demo rating. 
 
9 p.m. - CBS' repeat of "CSI: NY" won the 9 p.m. hour overall with 5.61 million viewers and finished third with a 0.8 rating among adults 18-49. NBC's "Grimm" rose to 5.31 million viewers and won the hour with a 1.6 key demo rating. ABC's "Primetime: What Would You Do?" was third with 4.33 million viewers and second with a 1.2 key demo rating. A second "Kitchen Nightmares" repeat averaged 2.06 million viewers and a 0.8 key demo rating. On The CW, the "Supernatural" finale was down week-to-week with 1.57 million viewers and a 0.6 key demo rating.
 
10 p.m. - A repeat of "Blue Bloods" won the 10 p.m. hour overall for CBS with 6.45 million viewers and finished third with a 0.8 rating among adults 18-49. NBC's "Dateline" was second overall with 4.755 million viewers and second with a 1.1 key demo rating. ABC's "20/20" won the hour in the key demo with a 1.2 rating and finished third overall with 4.425 million viewers.
 
All ratings information comes from preliminary Fast National Nielsen data, which includes live and same-day DVR viewing. All numbers are subject to change.