There’s a lot of data collected over many years and it all supports 85 as the median - which is the 50%ile. Who knows what the cause is.
Are they testing them for what they know, or if they are capable of processing information?
Regarding inner city blacks, I have no doubt they may not know much, nor are they expected to.
Do “they” differentiate between black ghetto types and middle class or professional blacks?
How about the IQs of British blacks...they seem far advanced over “African-Americans”...at least they can speak the language.
I think it’s cultural, since we see other blacks participating successfully in the American economy and as professionals.