It’s hard to find more info. I was trying to look at the iranian study, which has many subjects as well. I also found a couple other studies. This is the korean one posted here, it has more info though:
It also has links to a different, earlier korean study. That study reported the same average, but a larger standard deviation. It also has a link to a malaysian study. I’ve been trying to find info on that and I just couldn’t. So again, if people have access to these things, I’m interested in reading about it.