> ± a few percentage points The variance is a lot higher than that. Tons of web projects are for internal tools (controlled environment), for mobile first, or

> ± a few percentage points The variance is a lot higher than that. Tons of web projects are for internal tools (controlled environment), for mobile first, or in industries or language communities or countries or markets where the browser distribution is entirely different. So as a professional what you do is (1) measure, (2) reach a business decision about browser support, and only then (3) choose technologies. With polyfills and Babel, using new features in old browsers isn't really a problem, but it's unfortunate that this is often required, and it's unfortunate that Web development has become so fragmented by developers preferring to use tools built on the platform rather than authoring for the platform directly.