I'm wondering where that number comes from? I've seen this stat a few times recently but don't know where it came from.

Just doing a quick perusal of the top 5 projects listed at http://pypi-ranking.info/alltime

1 (boto) does not support 3.x

3 (distribute, zc.buildout and pip) only distribute non-version dependent files

leaving just 1 (lxml) with version dependent installers listed at all and it is only for the windows installers.

Drilling down into lxml, roughly 95% of its downloads are the version agnostic .tar.gz file. Also the version dependent installers do not include a 3.3 version but only 3.2 for python3. But even with only an installer for a old version of python3 available it still is >8% of version dependent downloads.