Which versions of internet explorer should I support?

Support from industry leaders

Jquery: IE 9+
Angular: IE9+
Bootstrap 4: IE9+
CSS Flexible Box Layout: IE11+
Google apps: IE11+
Microsoft: IE11+

Percentage of desktop users of internet explorer at June 2016

According to netmarketshare.com right now the percentage of desktop users of internet explorer is:
IE 11 22.05%
IE 10 3.40%
IE 9 4.32%
IE 8 6.87%
IE 7 0.63%

How many users you lose:

Conclussion

For most companies it makes sense at this time to support IE9+ but I'm in the process of learning CSS and trying to learn a hack-free one so I'm going the flexbox way and with that IE11+