Table 1.
Characteristics of the children of surveyed mothers.
| Preliminary Survey | Targeted Survey | |||
|---|---|---|---|---|
| n | % | n | % | |
| All | 19,041 | 2439 | ||
| Sex | ||||
| Boys | 9791 | 51.4 | 1236 | 50.7 |
| Girls | 9250 | 48.6 | 1203 | 49.3 |
| Grade 1 | ||||
| ES (1st-3rd) | 5264 | 27.6 | 590 | 24.2 |
| ES (4th-6th) | 4479 | 23.5 | 613 | 25.1 |
| JHS | 4291 | 22.5 | 618 | 25.3 |
| HS | 5007 | 26.3 | 618 | 25.3 |
| Residential area | ||||
| Hokkaido | 1078 | 5.7 | 145 | 5.9 |
| Tohoku | 1238 | 6.5 | 158 | 6.5 |
| Kanto | 6132 | 32.2 | 785 | 32.2 |
| Chubu | 3493 | 18.3 | 420 | 17.2 |
| Kinki | 3567 | 18.7 | 461 | 18.9 |
| Chugoku | 1137 | 6.0 | 145 | 5.9 |
| Shikoku | 489 | 2.6 | 63 | 2.6 |
| Kyusyu | 1907 | 10.0 | 262 | 10.7 |
| Household income 2 | ||||
| <2 million yen | 773 | 4.1 | 90 | 3.7 |
| 2–4 million yen | 3212 | 16.9 | 348 | 14.3 |
| 4–6 million yen | 4886 | 25.7 | 625 | 25.6 |
| 6–8 million yen | 3167 | 16.6 | 420 | 17.2 |
| 8–10 million yen | 1434 | 7.5 | 252 | 10.3 |
| 10–12 million yen | 633 | 3.3 | 98 | 4.0 |
| 12–15 million yen | 289 | 1.5 | 49 | 2.0 |
| 15–20 million yen | 98 | 0.5 | 22 | 0.9 |
| >20 million yen | 41 | 0.2 | 4 | 0.2 |
| No answer | 4508 | 23.7 | 531 | 21.8 |
1 ES: Elementary School, JHS: Junior High School, HS: High School; 2 An assumed exchange rate of 110 yen to one US dollar.