With swimming and gymnastics live in prime time, household ratings for the 2008 Beijing Games topped the 2004 Athens event by 8%. Based on one estimate, NBCU isn't so sure London will bring an increase in ratings. Yet the NBCU sales department may be playing it conservatively. Olympic viewership can be hard to predict. Compelling storylines can emerge unexpectedly, sparking national debates or patriotic surges, which can translate into higher Nielsen numbers.