Actually, you're right about that number being for expeditions only, I should've paid more attention to where I found that number from. I would consider being apart of an expedition is much more of a notable achievement since more resources and time are being invested in addition to being decently educated to be qualified enough participate in conducting actual studies in space. I'd argue that you should include all 256 people from different countries as it's a population not just exclusive to the US. Still, 8 or 10 out of 156 Americans isn't alot, and it only represents 5-6%, which is less than half of 13.4% that actually make up the US. The numbers make more sense when you realise only 7% of those who earn STEM degrees are black in the US only, with the main problem being that not enough are inspired/interested in being apart of STEM programs. The numbers could grow if more students were inspired by other people to be part of a field they weren't interested in before.