Table 1. Population characteristics: Japanese newborns in 2001 in the Longitudinal Survey of Babies in 21st Century, followed up until 2011.
| Boys | Girls | |
|---|---|---|
| N (%) | 16,403 (51.9) | 15,206 (48.1) |
| Income quartile, n (%) | ||
| 1 (lowest) | 4120 (25.1) | 3783 (24.9) |
| 2 | 4085 (24.9) | 3817 (25.1) |
| 3 | 4119 (25.1) | 3783 (24.9) |
| 4 (highest) | 4079 (24.9) | 3823 (25.1) |
| >30% negative income change during economic crisis, n (%) | 1531 (9.3) | 1482 (9.8) |
| >20% negative income change during economic crisis, n (%) | 2136 (13.0) | 2096 (13.8) |
| >10% negative income change during economic crisis, n (%) | 3225 (19.7) | 3083 (20.3) |
| Residential area, n (%) | ||
| 20 designated cities | 4209 (25.7) | 3868 (25.4) |
| Other cities | 10,640 (64.9) | 9908 (65.2) |
| Rural | 1505 (9.2) | 1377 (9.1) |
| Missing | 49 (0.3) | 53 (0.4) |
| Mother's age (SD) | 30.3 (4.3) | 30.3 (4.3) |
| Father's age (SD) | 32.5 (5.4) | 32.4 (5.3) |
| Missing, n (%) | 299 (1.2) | 313 (1.4) |
| Father's education, n (%) | ||
| Junior high school | 860 (5.2) | 789 (5.2) |
| High school | 6220 (37.9) | 5816 (38.3) |
| Vocational school | 2579 (15.7) | 2333 (15.3) |
| Higher education | 6332 (38.6) | 5896 (38.8) |
| Missing | 412 (2.5) | 372 (2.5) |
| Mother's education, n (%) | ||
| Junior high school | 418 (2.6) | 392 (2.6) |
| High school | 6108 (37.2) | 5771 (38) |
| Vocational school | 7120 (43.4) | 6420 (42.2) |
| Higher education | 2467 (15) | 2373 (15.6) |
| Missing | 290 (1.8) | 250 (1.6) |
| Single parent household, n (%) | 266 (1.6) | 246 (1.6) |
| Missing, n (%) | 5 (0) | 5 (0) |
| Three generation household, n (%) | 3781 (23.1) | 3388 (22.3) |