how is it normalized? every single thing I type in has an upward trend, which to me just suggests that interest in Hacker News has increased over the last few years... and I don't really need a chart to tell me that since I live in silicon valley :)
Btw - my suggestions got me thinking - I assumed this is looking at posts and comments. Whether just submission titles or if includes comments will affect best way to normalise.
So if say in q1 2011 there were 1m posts + comments, and in q1 2007 10k, multiply the count for q1 2007 by 100.
It would be truly great to have this normalisation optional, e.g option to normalise by comment+post count and maybe also normalise by number of users (could be an interesting comparison). And perhaps have them super-imposed on each other!
I'm storing the total hits so I will do the calculations on the client-side, which means I just might be able to add some toggles for the normalization schemes ;)
Check the "Learn More" section where I give you props for the help :)
Also, see my other comment below for a suggestion re filtering out crappy posts.
Your app looks a lot better, though! (And my dataset ends around Sept. of last year.)