Evidence From Standardization Samples

It is often asserted that Black Americans have made no IQ gains on White Americans. Until recently, there have been no adequate data to measure trends in Black IQ. We analyzed data from nine standardization samples for four major tests of cognitive ability. These data suggest that Blacks gained 4 to 7 IQ points on non-Hispanic Whites between 1972 and 2002. Gains have been fairly uniform across the entire range of Black cognitive ability. No one can really trace the Black-White IQ gap in the United States back to its origins. Estimates for 1917 and 1943 are based on military data subject to a host of biases, and estimates since 1945 are based almost entirely on averaging studies, none of which compared nationally representative samples taking the same test at two different times (Herrnstein & Murray, 1994). Rushton and Jensen (2005) recently stated that the IQ difference between Black and White Americans stands at 1.1 standard deviations and is as large today as it was nearly 100 years ago. We believe that the racial IQ gap may have been about 1.1 standard deviations in the late 1960s. Two data sets from nationally representative samples, the data of the 1965 Coleman Report (Jensen, 1980, p. 479) and the standardization data for the 1972 Wechsler Intelligence Scale for Children–Revised (WISC-R; Harcourt Assessment, 2005b), yield an average Black-White IQ gap of 1.108 standard deviations. More recently, Flynn (1987) analyzed military data and found that Blacks gained 3 points on Whites between 1940 and 1960, but this estimate was tentative.