Table 1 Descriptive statistics: sex, parental social class and personal income (quartiles) distributions and smoking prevalence at ages 11, 13 and 15.
| Aged 11 | Aged 13 | Aged 15 | |
|---|---|---|---|
| No (%) | No (%) | No (%) | |
| Sex | |||
| Male | 1335 (51.6) | 1222 (51.5) | 1116 (50.8) |
| Female | 1251 (48.4) | 1149 (48.5) | 1080 (49.2) |
| Social class | |||
| I | 135 (5.7) | 129 (5.9) | 125 (6.1) |
| II | 570 (24.0) | 542 (24.6) | 523 (25.4) |
| IIIn | 323 (13.6) | 303 (13.7) | 284 (13.8) |
| IIIm | 781 (32.9) | 718 (32.6) | 665 (32.3) |
| IV | 402 (16.9) | 366 (16.6) | 336 (16.3) |
| V | 165 (6.9) | 146 (6.6) | 127 (6.2) |
| (Missing) | 210 (8.1) | 167 (7.0) | 136 (6.2) |
| Personal income | |||
| Quartile 1 | 522 (20.2) | 512 (22.0) | 469 (21.9) |
| Quartile 2 | 846 (32.8) | 577 (24.8) | 652 (30.4) |
| Quartile 3 | 583 (22.6) | 737 (31.7) | 578 (26.9) |
| Quartile 4 | 629 (24.4) | 498 (21.4) | 447 (20.8) |
| Smoking | |||
| Ever | 347 (13.4) | 1229 (51.9) | 1466 (66.8) |
| Current | 13 (0.5) | 277 (11.7) | 559 (25.5) |
| Regular | 3 (0.1) | 244 (10.3) | 481 (21.9) |
| Daily | 137 (5.8) | 388 (17.7) | |
| 5+ cigs/day | 36 (1.5) | 213 (9.7) | |
| Sample size | 2586 | 2371 | 2196 |