Situation: You love obscure facts about Project Management.
Oddly enough, we get asked this a lot. However there aren't a lot of good numbers to go by. PMI estimates that there 16.5 million Project Managers in the world. Both PMI and Gantthead have relationships with a bit more than 600K each, with roughly a 13% overlap. 66.8% of PMI members are based in North America. 53.9% of gantthead members are based in North America. So that implies that there may be 8.7M-11M Project Managers in North America.
Of course, these percentages shrink every year as the industry (and everything else in the world) becomes more global - but that's our "guesstimate".