TV Viewership Plummets?

There's an ungankable graph in today's NYT -- http://www.nytimes.com/imagepages/2010/01/17/business/17nbc_g.html -- in the middle of the left column -- showing the decline, starting in the 1950s, of network TV viewership. I emphasize the 50s, because cable does not seem to be the factor here. NBC primetime viewership -- similar to that of CBS -- has plummeted from a high, apparently, of 30 mill in 1950, nearly halved to 18 mill in 1960, with slight zigs and zags but consistently moving downward through the decades to 5 mill in 2010, with CBS, ABC and Fox, debuting in the early 90s, all in the under-10-mill tank.
This is big.

I wonder if movie viewership has plummeted similarly?

What are people doing instead? What did they start doing in the middle 1950s to cause such a huge 10 mill drop in prime time viewership, which declined consistently previous to the invention of cable, Fox and the net, and at a consistent rate after?

And, why is no one discussing the saccharine cultural ripoff by Cameron of cartoon Navajo? I have tried to get the Navajo at KWRK interested, and will have to try again.
http://bsnorrell.blogspot.com/2010/01/navajo-filmmaker-arlene-bomwn-avatar.html
http://io9.com/5422666/when-will-white-people-stop-making-movies-like-avatar
http://news.yahoo.com/s/ap/20100111/ap_on_en_mo/us_avatar_racism
http://www.essence.com/entertainment/hot_topics/does_sci-fi_blockbuster_avatar_have_a_ra.php