I’d love if Gainsight (or anyone) published something like this, but I’m not aware of it. 

Ask your CSM if you haven’t already, but my experience with getting benchmark data has been ¯\_(ツ)_/¯

I’ve been working with communities for a loooong time and can say at this point, I haven’t noticed any consistent percentage or benchmark. It all really depends on the product, the purpose, other services offered (customer success, support, chat, etc.) and even then, you have to consider the type of customer and the type of engagement they want/need.

So tl;dr - nope! Totally unique to each community.

I asked this question on a different community-related forum and no-one really had a good answer there either. There are so many variables. As a software company that sells site licenses, it’s very difficult to even know how many users we have! I’d guesstimate about 1%  to 2% have a community account. That’s an extremely rough number, but I think it’s that sort of order of number. I’d love to imagine it’s higher, but our community has been around for 20+ years, and there are many accounts that I assume are inactive.

I think I’d focus on quality, rather than quantity, because that’s something you have direct control over. It’s much easier to measure the percentage of members with a positive experience, and much easier to affect that number.