Very nice data and chart. What did you use to perform the analysis? Did you dump the chain to a DB? Query the bitcoind software directly? I'm interested in doing a bit of similar data mining, but need a pointer to get started.
Used a DB from
http://codesuppository.blogspot.co.uk/ You might find his blockparser useful. At coinometrics we are now using Bitcore and are working on dumping the chain into a DB as querying the blockchain directly for this information takes too long.