Flynn effect
The average rate of rise seems to be around three IQ points per decade. Today, children go to school for a longer time. They have also become more familiar with testing. It might therefore be expected that the biggest gains occur with school-related content, such as vocabulary, arithmetic or general information. Just the opposite is the case: abilities such as these have had small gains and occasional declines over the years. The largest changes appear  on general intelligence factor loaded (g-loaded) tests such as Raven's Progressive Matrices, instead. For example, Dutch soldiers gained 21 points in only 30 years, or 7 points per decade, between 1952 and 1982.