IQ tests are revised to meet the current generation’s standard deviation. When our current generation takes previous generation’s IQ tests, they almost always perform better than the previous generation. Fluid IQ (not academic smarts) scores have been drifting up 3 points per decade. This is used as an argument against Eugenics, saying that intellect has little correlation to genealogy.
Explanations
Equity Improvement
The advances in nutrition, healthcare and pedagogy increase IQ
Slowing Effect
This effect is slowing down, and eventually will reverse on itself.