We’ve linked the graphic above but encourage everyone to visit the source as well.
The most striking stat here is that out of the top one million websites, a whopping 12.4% run WordPress. That comprises over half of the market for content managed websites. Popularity isn’t always a key indicator of quality, but in this case it certainly is. With open source software, there’s no monetary reason to choose one platform over another. Quality quickly becomes a top metric when the software is free.