Table 1 Numbers of respondents and response rates (%) by age and sex in 1981–1983 and 1987–2003.
| 1981 | 1983 | 1987 | 1989 | 1991 | 1993 | 1995 | 1997 | 1999 | 2001 | 2003 | |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Age 12 | |||||||||||
| Boys | |||||||||||
| Respondents (n) | 483 | 450 | 414 | 406 | 426 | 399 | 395 | 427 | 442 | 351 | 368 |
| Response rate (%) | 88 | 85 | 81 | 76 | 77 | 73 | 78 | 76 | 79 | 72 | 69 |
| Girls | |||||||||||
| Respondents (n) | 514 | 440 | 367 | 430 | 399 | 437 | 424 | 440 | 407 | 425 | 390 |
| Response rate (%) | 92 | 91 | 83 | 82 | 82 | 84 | 86 | 87 | 85 | 82 | 75 |
| Age 14 | |||||||||||
| Boys | |||||||||||
| Respondents (n) | 488 | 429 | 1128 | 361 | 1196 | 1203 | 1177 | 1168 | 1187 | 1251 | 1092 |
| Response rate (%) | 87 | 78 | 81 | 75 | 74 | 74 | 75 | 69 | 74 | 66 | 66 |
| Girls | |||||||||||
| Respondents (n) | 548 | 482 | 1202 | 431 | 1337 | 1299 | 1301 | 1347 | 1313 | 1485 | 1245 |
| Response rate (%) | 92 | 86 | 90 | 90 | 86 | 86 | 85 | 84 | 85 | 79 | 78 |
| Age 16 | |||||||||||
| Boys | |||||||||||
| Respondents (n) | 535 | 413 | 1183 | 362 | 1008 | 1168 | 1232 | 1126 | 1110 | 892 | 1003 |
| Response rate (%) | 85 | 75 | 77 | 70 | 68 | 70 | 72 | 68 | 68 | 62 | 59 |
| Girls | |||||||||||
| Respondents (n) | 529 | 509 | 1284 | 380 | 1272 | 1389 | 1469 | 1379 | 1333 | 1138 | 1296 |
| Response rate (%) | 91 | 91 | 89 | 82 | 86 | 87 | 88 | 87 | 85 | 82 | 79 |
| Age 18 | |||||||||||
| Boys | |||||||||||
| Respondents (n) | 519 | 489 | 1134 | 328 | 893 | 1029 | 1071 | 1088 | 1112 | 774 | 570 |
| Response rate, % | 81 | 75 | 69 | 63 | 61 | 66 | 67 | 60 | 63 | 53 | 50 |
| Girls | |||||||||||
| Respondents (n) | 524 | 509 | 1401 | 407 | 1103 | 1265 | 1313 | 1415 | 1315 | 976 | 797 |
| Response rate (%) | 88 | 87 | 84 | 80 | 82 | 83 | 86 | 83 | 80 | 76 | 74 |
| Total | |||||||||||
| Respondents (n) | 4140 | 3721 | 8113 | 3105 | 7634 | 8189 | 8382 | 8390 | 8219 | 7292 | 6761 |
| Response rate (%) | 88 | 83 | 81 | 77 | 77 | 78 | 79 | 76 | 76 | 70 | 69 |