How I see it is that they are very careful with the statements they make. It seems to me like there was a study of this disorder in lower income communities in the uk, which leaded to the 2%. However, it is unreasonable to then draw the conclusion that it is also 2% in the entirety of the USA, or that it must be lower or higher.

Also, I think its still helpful to define a disorder even if you haven't researched globally how many people have it.

> The reason for my beef in here mainly that all the numbers are just stated, with no respect to what numbers are. And I would expect either an explanation of a numerical method to estimate this number, or a source as to where this number has been gotten from. I agree that it would be nice have references. However, if you are just diagnosing an illness, it probably doesn't matter that much how many people in the world have this illness, just if the person in front of you has it or not. So the people that are actually using this text don't really need the sources.

It seems to me like the main purpose of DSM-5 is to define a bunch of disorders, so everyone has a common language to talk about the actually useful stuff like treatments. So even if it mistakenly says 2% instead of 0.2%, that doesn't really matter, I think.

Also, even if it is non-obvious to us, there might still be someplace where sources are listed. (IE maybe if you look at some meeting notes of the author committee)