You could interpolate from the chart that shows distribution by browser versions up to February 2012. Chrome's auto-update feature is staggeringly efficient.

    IE 8.0         18.86
    IE 9.0         12.08
    IE 7.0          3.32
    IE 6.0          1.48

    Chrome 16.0    13.39
    Chrome 15.0     0.35
    Chrome 14.0     0.35
    Chrome 12.0     0.27
    Chrome 13.0     0.25

EDIT: removed the Firefox and "Other" numbers as their sum is nowhere close to the aggregated numbers in the browser monthly charts [2]. StatCounter must be counting recent versions of Chrome and Firefox as "Other" in data set [1].

Source:

[1] http://gs.statcounter.com/#browser_version-ww-monthly-201102... (from the CSV file)

[2] http://gs.statcounter.com/#browser-ww-monthly-201102-201203