About the numbers:
WordPress is used by a staggering 37.3% of English language websites [compared with 25% worldwide]
... we count the hosted sites only if they are reachable via their own domain (not only as subdomain of wordpress.com), and they must qualify like all other sites in our surveys by getting enough visitors on that separate domain to make it into the top 10 million Alexa sites. [ie. they are mostly enterprise sites] As a result, the vast majority of the millions of blogs at WordPress.com are not counted. Only 1.25% of the WordPress sites in our surveys are hosted by Automattic at WordPress.com. That makes the WordPress CMS market share even more remarkable.