Actually, NetMarketshare does provide that type of data.
IE6 has dwindled to 7% and IE7 would seem to be even less, as it's bundled into the stats for 'Other'. IE8 and IE9 are about the same, each in the mid 20's.
The problem with these stats however is the 'Other' figure of 53% which I would hazard a guess to say is caused by the rapid version changing of Chrome and Firefox. How can you gather stats for a browser version when it changes almost every week?