I absolutely agree with you regarding seasonality, I simply don't have a snapshot from a year ago. But a year from now I will be able to do this now that I am collecting the data each month.
Thanks for putting this together.
Also if you can't get your hands on the data from 2012 maybe taking the launch date vs their current Alexa position and averaging this out to see their Alexa growth over their lifespan. That would be really nice to see.