On my own (long abandoned) blog, about 20% of (public) posts seem to contain an em dash: https://shreevatsa.wordpress.com/?s=%E2%80%94 (going by 4 pages of search results for the em dash vs 21 pages in total).
On my own (long abandoned) blog, about 20% of (public) posts seem to contain an em dash: https://shreevatsa.wordpress.com/?s=%E2%80%94 (going by 4 pages of search results for the em dash vs 21 pages in total).