Figure 10.14: Examples of gains in intelligence-test scores Shown here are IQ gains from 1948 to 2002, in the United States, as measured by Raven’s Progressive Matrices, by the Wechsler Intelligence Scale for Children (Full Scale), and by several subtests of the Wechsler Intelligence Scale for Children. These are the gains that would have occurred if the tests were not made more difficult and the scoring systems were not adjusted at each test revision.
(Based on data in Flynn, 2007.)