Pretty off topic, but why would anyone ever stay on IE9? It means you are on > XP which means you should be able to upgrade to at least 10 I believe, if not 11. Is it just a lack of permissions to upgrade the browser combined with lazy administrators?
I don't know. Nearly all the IE9 users are on Win7.
If I had to guess, it's simply because upgrades are such a hassle in heavily regulated industries. (Above and beyond the typical hassles of an upgrade in any large enterprise.) I see similar numbers in Healthcare, for example, but not Education or Construction.
I keep meaning to do a blog post about the tech trends in different industries.
People should always run their own numbers. It can vary quite a bit from the internet-wide average.