Table 1.
Year | 1990 | 1991 | 1992 | 1993 | 1995 | 1996 | 1998 | 2000 |
Age | 13 | 14 | 15 | 16 | 18 | 19 | 21 | 23 |
N1 | 924 | 958 | 936 | 789 | 779 | 643 | 634 | 630 |
1 During the first two years of the study those families and students who moved to the district of the participating schools were invited to enrol into the study, thus the n increased the first two years.