Table 1 Sample characteristics. Years 2000-2010
Characteristic | 2000 | 2001 | 2002 | 2003 | 2004 | 2005 | 2006 | 2007 | 2008 | 2009 | 2010 |
|---|---|---|---|---|---|---|---|---|---|---|---|
N | 22,418 | 22,257 | 15,752 | 25,299 | 32,372 | 41,365 | 38,748 | 40,407 | 38,681 | 32,461 | 25,555 |
Age (mean±SD) | 17.1 ± 1.5 | 17.1 ± 1.4 | 17.2 ± 1.6 | 17.1 ± 1.6 | 17.1 ± 1.6 | 17.1 ± 1.6 | 17.1 ± 1.6 | 17.1 ± 1.6 | 17.2 ± 1.6 | 17.1 ± 1.6 | 17.1 ± 1.4 |
Gender (male) | 47.3% | 45.0% | 45.5% | 45.5% | 48.1% | 48.1% | 48.9% | 49.7% | 49.0% | 49.2% | 47.9% |
Response rate* | 100.0% | 87.1% | 98.6% | 94.9% | 96.1% | 94.1% | 88.9% | 92.4% | 85.8% | 89.2% | 86.2% |