Well duh comparing the graphs doesn't provide the answer. But it provides good negative evidence if hats worn declines before interstates, for example. And if the graphs are similar, its a piece of the puzzle towards the answer.

It's probably not a waste of time creating a graph that might increase understanding and create better questions?

Not to be too funny, but humans are great at finding patterns in pictures that don't exist.

http://static.flickr.com/54/139092366_ce5b410228_o.jpg

Suddenly hatless men found that they were getting sunburned. They needed cars in order to get quickly from one place to another.