Overnight Ratings
9x01, Nature of the Beast: 4.2/12, 19.55 million
9x02, Restless: 4.15/12, 19.181 million
9x03, The Penelope Papers: 4.1/12, 18.86 million
9x04, Enemy on the Hill: 3.9/11, 18.657 million
9x05, Safe Harbor: 3.8/10, 19.01 million
9x06, Thirst: 4.0/11, 19.05 million
9x07, Devil's Triangle: 3.9/11, 19.38 million
9x08, Engaged (Part 1): 4.1/11, 20.31 million
9x09, Engaged (Part 2): 4.0/11, 19.935 million
9x10, Sins of the Father: 3.5/10, 18.45 million
9x11, Newborn King: 3.5/10, 19.03 million
9x12, Housekeeping: 4.2/11, 20.015 million
Final Ratings
9x01, Nature of the Beast: 4.3/12, 19.96 million
9x02, Restless: 4.2/12, 19.51 million
9x03, The Penelope Papers: 4.2/12, 19.35 million
9x04, Enemy on the Hill: 4.0/11, 18.98 million
9x05, Safe Harbor: 3.9/11, 19.41 million
9x06, Thirst: 4.1/12, 19.43 million
9x07, Devil's Triangle: 3.9/11, 19.71 million
9x08, Engaged (Part 1): 4.1/11, 20.38 million
9x09, Engaged (Part 2): 4.0/11, 20.00 million
9x10, Sins of the Father: 3.5/10, 18.45 million
9x11, Newborn King: 3.6/10, 19.13 million
9x12, Housekeeping: 4.1/11, 19.81 million
1. Sorry for not posting the ratings for Newborn King the day after it aired; I just completely spaced out. I added the information to the archives above.
2. TV By The Numbers hasn't posted the Tuesday Final ratings yet; as soon as I see them, I'll edit this entry and add the information. ETA: Info has been added; NCIS was adjusted down in the overnights. Even without them, it's easy to see that the episodes that aired right around the holidays suffered, and that it helps to air new episodes in January, when there are lots of reruns. (I suspect this is part of why CBS always orders a couple of extra episodes of NCIS; it gives them something to air while the other networks have to hold new episodes until February sweeps.)
3. The Nielsen Company released its list of Top Ten Regularly Scheduled Programs of 2011 (read: series, not specials); the only scripted shows in the top ten were NCIS and NCIS:LA.
1. American Idol-Wednesday, Fox, 8.1 rating (persons 2+), 23.9 million total viewers
2. American Idol-Thursday, Fox, 7.5 rating, 22.0 million
3. Sunday Night Football, NBC, 7.1 rating, 20.5 million
4. Dancing with the Stars, ABC, 6.7 rating, 19.6 million
5. Dancing with the Stars Results, ABC, 5.8 rating, 16.9 million
6. Sunday Night NFL Pre-Kick, NBC, 5.5 rating, 15.9 million
7. NCIS, CBS, 5.2 rating, 15.2 million
8. NFL Regular Season, ESPN, 4.5 rating, 13.1 million
9. The OT, Fox, 4.4 rating, 12.9 million
10. NCIS: Los Angeles, CBS, 4.3 rating, 12.6 million
Since this is going by the calendar year, not the broadcast-network season, this data is from the back half of Season 8 and the front half of Season 9. Also, it looks like the rating is not the Adults 18-49 demographic, but "Persons 2+," which might be literally "Anyone older than two years." (I'm still researching this; look for more info as I find it.) This list represents how much viewing patterns have changed since the advent of the DVR and online viewing; people just don't watch scripted shows live much anymore.
The source is
here, but I copy-and-pasted the information from a TV Week recap of the Nielsen information because it was presented in a format that was easier to carry over here.
There are some other tables at the Nielsen link above that you might find interesting, even though NCIS doesn't appear on them. (#1 Most Timeshifted Series: American Horror Story.)