I think a bit more interesting statistics is to count only \w—\w. This excludes cases like "(—)" and emdashes surrounded by spaces, which is, apparently, what Russian-speaking users like to use. Also it is an very old tradition to format page titles as <title>[Page name] — [Website name]</title>: depending on language this is a default setting for MediaWiki, WordPress, etc.

Not just Russian speakers put spaces around the emdash, but also the AP style guide.

Also, for what it's worth, UK style guides recommend endash + spaces (but many write emdash + spaces instead), and so do some other languages (eg. German). There are more countries than just America and Russia!