It’s not about percentages, it’s about numbers. We don’t actually go out of our way to support it on pages and we don’t tell other departments to test in it, but if you’re building a pattern library it makes sense to do the hard work up front. In terms of graceful degradation, yep. In our current patterns project we’ve dropped all JS for IE7 beyond the HTML5shim.

Our support schedule is at https://www.gov.uk/service-manual/technology/designing-for-d...