Yeah, I would like to see numbers for just a random sample of the general population.......although, the numbers that they presented might give a glimpse. They reported...
110 of 111 former NFL players
48 of 53 former college players
3 of 14 former high school players
That would suggest that the rate goes up as the level of play goes up, although the numbers are skewed since the sample is a voluntary sample. If you are concerned that you have CTE, then you probably have a higher than normal chance of having CTE. But even with skewed numbers, it seems that the rate does go up at higher levels of play, just maybe not as much as these numbers would indicate. That could be for two reasons that I can think of. The first reason is the cumulative effects of playing for a longer time period. The second reason is harder, more violent hitting at the higher levels of play.
The other thing that I would like to know is more specific information about the high school players that were studied, since they are the closest thing that we have to a sample of the general population. Were these players that played in high school, stopped playing after high school, lived their lives, and then died at a normal age? Or were these former players that died young for some reason? If they are players that died young, then it is possible that the reason that they have a lower rate of CTE is simply because they are younger than the other people studied. Maybe people naturally develop CTE as they age. It might have nothing to do with football. On the other hand, if they died at a normal age, then it has been 50+ years since they played football. High school football has changed quite a bit in the past 50+ years. So I would imagine that rate will probably go up if you fast forward to the point where today's high school players are dying.
All of this is why numbers for sample groups that have nothing to do with football would be useful to compare against. A random population sample, people that jog every day, people that operate jackhammers on construction sites, human cannonballs, etc.