"The Bell Curve: Intelligence and Class Structure in American Life" (1994) is a controversial bestseller that Charles Murray wrote with Harvard professor Richard J. Herrnstein. The book's title comes from the bell-shaped normal distribution of IQ scores. Its central thesis is that intelligence is a better predictor of many factors including financial income, job performance, unwed pregnancy, and crime than one's parents' socio-economic status or education level. The book also argued that those with high intelligence (the "cognitive elite") are becoming separated from those with average and below-average intelligence, and that this constituted a dangerous social trend.