Table 1.
Demographic Characteristics of Chinese Children and Adolescents (N = 595,057)
| Variables | N (%) | |
|---|---|---|
| Gender | ||
| Boy | 3,24,932 (54.6) | |
| Girl | 2,70,125 (45.4) | |
| Age (year, mean ± SD) | 12.8 ± 2.0 | |
| Ethnic group | ||
| Han | 5,77,205 (97.0) | |
| Minority | 17,852 (3.0) | |
| School category | ||
| Primary school | 2,26,121 (38.0) | |
| Junior high school | 2,54,089 (42.7) | |
| Senior high school | 1,14,847 (19.3) | |
| Grade (age [years], mean ± SD) | ||
| Grade 1 (7.26 ± 1.09) | 1,190 (0.2) | |
| Grade 2 (8.11 ± 0.98) | 1,785 (0.3) | |
| Grade 3 (9.35 ± 1.12) | 1,796 (0.3) | |
| Grade 4 (10.44 ± 0.89) | 1,856 (0.3) | |
| Grade 5 (11.40 ± 0.56) | 1,13,060 (19.0) | |
| Grade 6 (12.37 ± 0.44) | 1,06,515 (17.9) | |
| Grade 7 (13.30 ± 0.39) | 91,638 (15.4) | |
| Grade 8 (14.29 ± 0.45) | 89,258 (15.0) | |
| Grade 9 (15.32 ± 0.37) | 72,596 (12.2) | |
| Grade 10 (16.24 ± 0.42) | 59,505 (10.0) | |
| Grade 11 (17.28 ± 0.51) | 53,555 (9.0) | |
| Grade 12 (18.24 ± 0.79) | 2,303 (0.4) | |
N, number; SD, standard deviation.