Millions of words have been written on IQ, but I have just watched a TV program called 'Race and Intelligence, Science's Last Taboo' (watch on the net on 'Channel 4 Catch Up'). The argument is that blacks have a lower IQ than whites who have a lower IQ than 'East Asians'. After the initial bigotry (by James Watson and others) presenter Rageh Omar, himself a Somalian, suggested that a lower IQ was more a lack of mental stimulation than skin colour, which I would agree.
IQ for whites - average 100.
IQ for 'east asians' - average > 100.
IQ for blacks - average < 100.
I assume that east asia is SE China, Hong Kong and Singapore. In other words Chinese ethnicity.
I'm no expert on this, but I have noted that on visits to HK that there appears to a certain environment where IQ flourishes, and that's in an area of high population density where there is wealth, law and order and access to high quality education.