The very first sentence in the section I pointed to in that link I offered:
Originally Posted by cr4zybe4utifu1
To even neglect 5% of your business would be insane, IE as a total are 55%. According to the stats gathered by that source 31% of browsers are still IE8.
Roughly 55% use IE-based browsers, with the percentage dropping very slowly.
Also, I assume your revenue comes from people not in the states. In which case IE becomes an even larger share because it's much more popular outside of North America.