Table 1: Number of adolescents in the cleaned research data and response rates (%) by gender and survey year.

1994 1998 2002 2006 2010 Number of adolescents Boys 576 770 870 781 992 Girls 618 775 875 889 1090 Total 1194 1545 1745 1670 2082 Response rate (%) Boys 89 89 87 83 94 Girls 99 99 92 86 97 Total 89 88 88 85 96