When I run deep in tournaments I normally check their OPR ratings. I've found that players with less than 90% (meaning they are in the best 10% of players) very rarely have a positive ROI (I only consider players with a decent samplesize: 1000+ tournaments played).

And only players with 99%+ constantly appear with ROIs of 25%+.

This means that you need to be top 10% to be profitable and to top 1% to be very profitable.

I made these observations on pokerstars.eu mostly. On this site I've also noticed that even the sickest pros with 99,98%+ ratings very rarely have higher ROIs than 40%.

On other sites, especially carbon, but also fulltilt and french-stars it seems that there are more players with 85%+ rankings that seem to be profitable, even over larger samples.

For concrete numbers: On pokerstars.eu there are sometimes 200k+ players playing at once. I guess more than 400k play there from time to time. Of all these I would estimate that about 10k are winning MTT (!) regulars in the long run. My guess for a global number would be something like 30000 – 90000 profitable regular MTT players (=pros).

Any one else who wants to guess?

I am surprised at this estimate that only 10% of players are still able to make a long term profit.  I thought it was like that a long time ago, and would have assumed that by now things have evened out a bit.  My guess would have been something like 15-20% are profitable, but I am silly.