APPENDIX 1

Socioeconomic Characteristics of Study Sample With Mother-Reported Data on Behavioral Difficulties Compared With Those Lost to Follow-Up

Lost to Follow-Up (n = 6831)Excluded or Missing Covariates (n = 1491)Analyzed Sample (n = 10 230)
Family type
 2 parent78.686.390.3
 1 parent21.413.79.7
Family income
 £52 000 or more4.65.67.9
 £31 200–£51 99910.212.819.8
 £20 800–£31 19915.717.723.7
 £10 400–£20 79930.130.428.6
 Less than £10 40030.023.914.1
 Not known9.39.65.9
Highest parental qualification
 Higher degree5.67.18.2
 First degree or diploma26.931.942.9
 A/AS levels16.114.816.3
 GCSE grades A–C28.020.723.4
 GCSE grades D–G7.56.94.2
 Other or overseas2.33.90.9
 None13.614.84.1
Highest parental occupational class
 Managerial or professional16.018.826.3
 Intermediate11.510.413.6
 Small employer or self-employed6.98.29.8
 Low supervisory or technical9.39.810.2
 Semiroutine or routine48.845.937.6
 Refused or missing7.56.82.5