Table 1. Demographic Information.
| Items | n | % |
| Gender | ||
| Boys | 157 | 48.8 |
| Girls | 165 | 51.2 |
| Siblings | ||
| No | 171 | 53.1 |
| Yes | 149 | 46.3 |
| No answer | 2 | 0.6 |
| Family type | ||
| Nuclear family | 279 | 86.6 |
| Extended family | 36 | 11.2 |
| No answer | 7 | 2.2 |
| Mother’s age | ||
| 20–29 | 99 | 30.7 |
| 30–39 | 209 | 64.9 |
| 40–49 | 13 | 4.0 |
| No answer | 1 | 0.3 |
| Father’s age | ||
| 20–29 | 74 | 23.0 |
| 30–39 | 202 | 62.7 |
| 40–49 | 27 | 8.4 |
| 50– | 4 | 1.2 |
| No answer | 15 | 4.7 |
| Mother’s career | ||
| No | 167 | 51.9 |
| Yes | 155 | 48.1 |
| Mother’s education | ||
| Middle school | 9 | 2.8 |
| High school | 70 | 21.7 |
| Vocational school | 66 | 20.5 |
| Short-term college | 83 | 25.8 |
| University | 86 | 26.7 |
| Post-college | 3 | 0.9 |
| No answer | 5 | 1.6 |
| Father’s career | ||
| No | 1 | 0.3 |
| Yes | 321 | 99.7 |
| Father’s education | ||
| Middle school | 6 | 1.9 |
| High school | 106 | 32.9 |
| Vocational school | 43 | 13.4 |
| Short-term college | 6 | 1.9 |
| University | 119 | 37.0 |
| Post-college | 23 | 7.1 |
| No answer | 19 | 5.9 |
| Family Income | ||
| <2 million JPY | 14 | 4.3 |
| 2–4 million JPY | 88 | 27.3 |
| 4–6 million JPY | 138 | 42.9 |
| 6–8 million JPY | 43 | 13.4 |
| 8–10 million JPY | 17 | 5.3 |
| ≧10 million JPY | 15 | 4.7 |
| No answer | 7 | 2.2 |
| Total | 322 | 100.0 |
JPY, Japanese yen.