Source: http://www.netmarketshare.com/
31% is not justification enough to maintain legacy code in a library that has become a little bloated over the years because of the backwards compatibility with older browsers. If you want to support that 31%, use the 1.9 branch it's better than the alternative being no support whatsoever.
Edit: Why all of the down-votes, is my response offensive?
Because you described "1/3 of the internet" as "a miniscule proportion of ones' users", probably.
StatCounter tracks 3 million websites vs 40k for NetMarketShare.
[1] http://gs.statcounter.com/
[2] http://gs.statcounter.com/#browser_version_partially_combine...
[3] http://gs.statcounter.com/#browser_version_partially_combine...
Well one of the websites I'm working on is a fairly big one in germany and only about 4% of all visitors are using IE8 or below. Guess what! We now only support IE9+.
If you think about it, there is no real reason not to support old browsers, unless you are in online gaming, of course.