Ashkenazi Jews have the highest average IQ of any ethnic group for which there are reliable data. They score 0.75 to 1.0 standard deviations above the general European average, corresponding to an IQ 112-115. This has been seen in many studies (Backman, 1972; Levinson, 1959; Romanoff, 1976), although a recent review concludes that the advantage is slightly less, only half a standard deviation Lynn (2004).
The fact that none of the cited sources (Backman, 1972; Levinson, 1959; Romanoff, 1976) provide evidence of or back the that Ashkenazi IQ is close to a standard deviation above the European average might be why that paper is controversial.
