Language fallback

Looks like you're right. ;-) I also see that 91 % of traffic from Belarus goes to the Russian Wikipedia; only 1 % ends up visiting the Belarusian Wikipedia. https://stats.wikimedia.org/wikimedia/squids/SquidReportPageViewsPerCountryBreakdownHuge.htm On the other hand, only 20 % of the traffic to the Belarusian Wikipedia comes from Belarus! https://stats.wikimedia.org/wikimedia/squids/SquidReportPageViewsPerLanguageBreakdown.htm#Belarusian

So it seems extremely likely that users of the Belarusian interface are equally comfortable with Russian.

Well, just bear in mind what I've told you about the 2nd group. BTW, re first posts here, be isn't "between" anything, it's just a language in its own right; just that its literary extension has never caught on.

Sure, I was just quoting what Ethnologue says.