Ratings for the Olympics through the first Thursday of competition, dating back to 1988. The average for the 1988 Seoul Olympics is only through six days, as the Opening Ceremonies that year took place on a Saturday.
2008, Beijing
18.8/34: Opening Ceremony (Fri., 8/9 NBC)
13.9/27: Day 2 (Sat., 8/10 NBC)
18.1/31: Day 3 (Sun., 8/11 NBC)
17.6/29: Day 4 (Mon., 8/12 NBC)
19.9/34: Day 5 (Tue., 8/13 NBC)
16.7/28: Day 6 (Wed., 8/14 NBC)
17.9/31: Day 7 (Thu., 8/15 NBC)
Average: 17.7/30
2004, Athens
14.4/26: Opening Ceremony (Fri., 8/13 NBC)
11.7/23: Day 2 (Sat., 8/14 NBC)
15.4/26: Day 3 (Sun., 8/15 NBC)
16.6/27: Day 4 (Mon., 8/16 NBC)
18.3/30: Day 5 (Tue., 8/17 NBC)
17.3/29: Day 6 (Wed., 8/18 NBC)
19.3/32: Day 7 (Thu., 8/19 NBC)
Average: 16.2/28
2000, Sydney
16.1/29: Opening Ceremony (Fri., 9/15 NBC)
13.1/25: Day 2 (Sat., 9/16 NBC)
14.6/24: Day 3 (Sun., 9/17 NBC)
13.8/23: Day 4 (Mon., 9/18 NBC)
15.5/26: Day 5 (Tue., 9/19 NBC)
14.6/25: Day 6 (Wed., 9/20 NBC)
14.9/26: Day 7 (Thu., 9/21 NBC)
Average: 14.6/25
1996, Atlanta
23.6/45: Opening Ceremony (Fri., 7/19 NBC)
17.2/37: Day 2 (Sat., 7/20 NBC)
22.9/42: Day 3 (Sun., 7/21 NBC)
22.9/40: Day 4 (Mon., 7/22 NBC)
27.2/40: Day 5 (Tue., 7/23 NBC)
22.4/41: Day 6 (Wed., 7/24 NBC)
26.8/48: Day 7 (Thu., 7/25 NBC)
Average: 23.4/43
1992, Barcelona
13.8/29: Opening Ceremony (Sat., 7/25 NBC)
18.1/33: Day 2 (Sun., 7/26 NBC)
19.7/36: Day 3 (Mon., 7/27 NBC)
20.5/37: Day 4 (Tue., 7/28 NBC)
18.9/35: Day 5 (Wed., 7/29 NBC)
22.2/40: Day 6 (Thu., 7/30 NBC)
Average: 19.0/35
1988, Seoul
15.2/29: Opening Ceremony (Fri., 9/16 NBC)
15.6/30: Day 2 (Sat., 9/17 NBC)
17.7/30: Day 3 (Sun., 9/18 NBC)
18.1/30: Day 4 (Mon., 9/19 NBC)
16.9/30: Day 5 (Tue., 9/20 NBC)
18.1/30: Day 6 (Wed., 9/21 NBC)
20.1/36: Day 7 (Thu., 9/22 NBC)
Average: 17.2/31
