After this, I'm off the fecundity kick for awhile, promise. In the following graph, GSS respondents are broken up into five categories; Really Smarts (wordsum score of 9-10, comprising 13% of the population), Pretty Smarts (7-8, 26%), Normals (6, 22%), Pretty Dumbs (4-5, 27%), and Really Dumbs (0-3, 12%). The average number of children middle-aged adults in each category have are shown by year. To avoid English language fluency issues, only those born in the US are included:
No surprises. There is some expected year-to-year bouncing around due to randomness, but the societal patterns are clear: Those on the left side of the IQ spectrum have more children than those on the right side do, and everybody has been having fewer and fewer of them over the last four decades.
GSS variables used: WORDSUM(0-3)(4-5)(6)(7-8)(9-10), YEAR, BORN(1), AGE(36-62), CHILDS