The cutoff should be 80 users. Averaged over multiple years. Even as pro-merge, it would be unfair to fold countries that actually fill 5 leagues
The problem is that the 'users' as per advertised is often quite inaccurate. Japan's advertised as having 26 users... yet opening each league page (JBBL; 4x Div IIs), that number is revealed to be 25 - and 3-5 of those are *not active*, and well on the way to becoming botified. So... 20ish.
Depending on what you declare as "active", we probably have maybe a dozen relatively active managers. If that.
http://with-malice.com/ - The half-crazed ramblings of a Lakers fanatic in Japan