The bottom line: economic growth has made us smarter. We can see this in the dramatic rise in education levels. Back in 1900 only about 6 percent of young Americans graduated high school, compared to 75 percent today. Back in 1950, only 8 percent of young Americans completed college, compared to 32 percent today. We can also see it in the "Flynn effect": the remarkable rise in raw IQ scores over time. And we can see it in the transformation of how we work. Back in 1900 almost 80 percent of working Americans were farmers, manual laborers, or domestic servants; today, some 60 percent work in white-collar office jobs. Back then, managers and professionals – i.e., the most cognitively demanding occupations that dominate the socioeconomic elite – comprised only 10 percent of the workforce; today, they account for 35 percent.
When I say we’re getting smarter, what I really mean is we are becoming more fluent in highly abstract ways of thinking. Abstraction is the master strategy for coping with complexity: broad categories and general rules are the mental shortcuts we use to keep information overload at bay.