For the first time, the number of channels "receivable" by the average TV household shot up past 100, jumping to 104.2 in 2006, up from 96.4 in 2005. But the number actually tuned by the average household remained about the same, moving to 15.7 in 2006 from 15.4 in 2005 and 15.0 in 2004, the first year for which Nielsen reports that statistic.

That pattern isn't surprising to television researchers who have long known that people will only watch a limited number of channels regardless of how many options are available to them. But the pattern also raises big implications for the concept of audience shares as Nielsen begins expanding the kinds of channels it tracks via its so-called A2/M2 (Anytime/Anywhere) initiative, including online, mobile, personal and out-of-home video platforms.

Just within the relatively limited conventional TV universe, the share of channels actually viewed has declined by about a percentage point in the past year.

On the bright side, Americans appear to be spending more time watching conventional TV options, despite the increasing availability of new video platforms. The average TV household spent 57 hours and 37 minutes watching TV each week in 2006, an increase of 20 minutes over 2005, and nearly 10 hours more per week than when Nielsen began using people meters two decades ago.

The time spent watching TV by the average person rose to 32 hours and five minutes in 2006, also up 20 minutes from 31 hours and 45 minutes in 2005.