http://en.wikipedia.org/wiki/Race_and_intelligence#Test_scores
Most of the evidence of intelligence differences between racial groups is based on studies of IQ test scores, almost always using self-reported racial data. Self-reports have been shown to be reliable indicators of genetic race to the extent that they match up with genetic clusters derived from mathematical clustering techniques, but these techniques do not determine whether these clusters themselves have any relation to intelligence.[16] According to psychologist David Rowe, self-report is the preferred method for racial classification in studies of racial differences because classification based on genetic markers alone ignore the "cultural, behavioral, sociological, psychological, and epidemiological variables" that distinguish racial groups.[40]
There are observed differences in average test score achievement between racial groups, which vary depending on the populations studied and the type of tests used. In the United States, self-identified Blacks and Whites have been the subjects of the greatest number of studies. Black-White average IQ differences appear to increase with age, reaching an average of nearly 17 points by age 24, which is slightly more than 1 standard deviation.[41] The Black-White IQ difference is largest on those tests that best represent the general intelligence factor g.[42] Using data primarily from the United States and Europe, Jensen and Rushton have estimated the average IQ of Blacks/Africans to be around 85; of whites/Europeans to be around 100, and of East Asians to be around 106.[3] Estimates from other researchers are more or less similar.[5][41] Gaps are also seen in other tests of cognitive ability or aptitude, including university admission exams, military aptitude tests and employment tests in corporate settings.[43]
The American Psychological Association has concluded that the racial IQ gap is not the result of a simple bias in the content or administration of tests, and the tests are equally valid predictors of achievement for Black and White Americans.[5] Arthur Jensen has found that when black and white individuals are matched for IQ, their relatives tend towards different means.[44][45]
The IQ distributions of other racial and ethnic groups in the United States are less well studied. The few Amerindian populations that have been systematically tested, including Arctic Natives,[46][47] tend to score worse on average than White populations but better on average than Black populations.[43] East Asian populations score higher on average than White populations in the United States as they do elsewhere.[16]