Betting on Superbowl viewers

So, I just found out that the Wiki articles on each superbowl list the cost of a 30 second commercial and the number of viewers.

Since advertising prices are set beforehand, they could be interpreted as marketers' estimates of the number (and hence value to sellers) of viewers watching the game. I wonder how well correlated prices are to viewership.

I'm thinking change in the real cost of a 30 second add from one year to the next should correlate to the change in number of viewers from one year to the next (or perhaps the change in the percentage of the population that is viewing the game.) There could be an argument for change in viewership of the preceding superbowls would be the driving factor, but I think the popularity of the teams in the current championship and the success of the current season has more impact on viewership than the previous superbowl.

So, some time in the near future, I think I'll try to throw some math at that data and see if there's much correlation.

(And yeah, I need to finish up the gaming analysis post, too. Not to mention health care that I got started on.)