Chapter 15, The Demography of Intelligence, Chapter 16, Social Behavior and the Prevalence of Low Cognitive Ability, Chapter 17, Raising Cognitive Ability Summary and Analysis

Various demographic trends are probably causing IQs to fall in the United States, and these trends will have consequences. First, modernization reduces birth rates which fall faster for the educated rather than the uneducated. For this reason, a downward shift in ability occurs on average; this is exacerbated by the fact that educated women have babies later.

A professional consensus exists in the United States that these downward pressures have operated either through most or all of the century. Women in all races and ethnicities follow this pattern, and blacks and Latinos are the most affected which could produce further gaps in achievement.

Immigration rules...