sample appears to remain reasonably representative of the U.S. population born in 1959–1965. The sample consisted of 227 families with sibships ranging from 2 to 5 offspring per family (592 individuals) and 479 individuals without siblings in the sample. 48.1% of subjects were male and 51.9% female, frequencies of minorities were reflective of the US population in 1976 with 80.3% White, 12.3% African American, and 5.4% of Hispanic or other ancestry. Additional summary statistics are given in Table 1.
