TABLE 1.

Demographic Characteristics of Subjects and Their Families at Enrollment (%)*

Sex
 Male48.7
 Female51.3
Birth order
 First child42.7
 Other57.3
Household income
 ≤$99994.7
 $10 000–$19 9998.3
 $20 000–$29 99914.8
 $30 000–$39 99920.9
 $40 000–$49 99916.7
 $50 000–$59 99912.5
 ≥$6000019.0
 Unknown3.3
Mother’s age
 16–2417.1
 25–2931.9
 30–3431.3
 35+19.6
 Unknown
Father’s age
 16–246.5
 25–2927.1
 30–3432.9
 35+27.0
 Unknown6.5
Mother’s education
 <12 y2.3
 High school/GED17.0
 Some college19.0
 2 y college15.4
 4 y college29.1
 Grad/professional17.1
 Unknown
Father’s education
 <12 y2.2
 High school/GED23.5
 Some college15.4
 2 y college12.5
 4 y college25.6
 Grad/professional15.7
 Unknown5.1
  • * N = 642 subjects.