The “Flynn effect” refers to a pattern observed by James Flynn, a professor at the University of Otago in New Zealand. It points out that for most of the 20th century, scores on IQ tests have been rising. The reasons behind this pattern have been a subject of controversy. For example, are the rising IQ scores a result of some factor like improved nutrition, both prenatally and for young children? Are they a result of improved schooling? Or a job environment that puts greater emphasis on cognitive skills? Is there something about the design of IQ tests, perhaps combined with that has made scores go up even if underlying intelligence hasn’t moved?
More here – Conversable Economist
PS: So it’s not just me that has noticed that people are getting thicker