Study population characteristics
| Year | Total | |||||||||
| 1999 | 2000 | 2001 | 2002 | 2003 | 2004 | 2005 | 2006 | 2007 | ||
| n | 8749 | 8112 | 9541 | 8574 | 8524 | 9407 | 9919 | 12 100 | 10 308 | 85 234 |
| Sex, % (n) | ||||||||||
| Boy | 50.8 (4444) | 51.0 (4140) | 51.3 (4891) | 50.6 (4337) | 51.1 (4358) | 50.8 (4776) | 50.4 (5003) | 51.2 (6193) | 50.7 (5224) | 50.9 (43 366) |
| Girl | 49.2 (4305) | 49.0 (3972) | 48.7 (4650) | 49.4 (4237) | 48.9 (4166) | 49.2 (4631) | 49.6 (4916) | 48.8 (5907) | 49.3 (5084) | 49.1 (41 868) |
| Ethnicity, % (n) | ||||||||||
| Dutch | 61.1 (5349) | 57.1 (4636) | 57.2 (5458) | 60.0 (5147) | 60.3 (5141) | 57.7 (5424) | 61.4 (6086) | 60.8 (7359) | 56.2 (5793) | 59.1 (50 393) |
| Turkish | 14.4 (1260) | 17.5 (1416) | 17.5 (1672) | 16.5 (1413) | 16.1 (1372) | 16.8 (1583) | 16.0 (1591) | 16.3 (1975) | 18.3 (1889) | 16.6 (14 171) |
| Moroccan | 12.1 (1063) | 13.4 (1086) | 13.9 (1322) | 12.0 (1032) | 12.4 (1054) | 13.8 (1298) | 12.0 (1193) | 12.1 (1469) | 14.4 (1480) | 12.9 (10 997) |
| Surinamese South Asian | 12.3 (1077) | 12.0 (974) | 11.4 (1089) | 11.5 (982) | 11.2 (957) | 11.7 (1102) | 10.6 (1049) | 10.7 (1297) | 11.1 (1146) | 11.3 (9673) |
| Age group, % (n) | ||||||||||
| 3–6 years | 64.0 (5596) | 68.9 (5586) | 66.8 (6374) | 70.6 (6055) | 79.6 (6784) | 77.1 (7252) | 69.2 (6865) | 57.6 (6965) | 48.1 (4959) | 64.0 (5596) |
| 7–10 years | 30.6 (2681) | 24.4 (1982) | 27.0 (2576) | 25.9 (2218) | 17.3 (1474) | 9.1 (858) | 16.5 (1639) | 21.9 (2646) | 31.8 (3283) | 22.7 (19 357) |
| 13–16 years | 5.4 (472) | 6.7 (544) | 6.2 (591) | 3.5 (301) | 3.1 (266) | 13.8 (1297) | 14.3 (1415) | 20.6 (2489) | 20.0 (2066) | 11.1 (9441) |
| Response, % | 82.3 | 78.7 | 84.8 | 84.5 | 83.2 | 83.2 | 84.5 | 85.6 | 79.9 | 83.0 |