Year	Cases per 100,000
1990	9.3
1991	11.8
1992	14.1
1993	16.2
1994	18.2
1995	19.9
1996	21.2
1997	22.3
1998	23
1999	23.3
2000	23.4
2001	23.2
2002	22.8
2003	22.2
2004	21.4
2005	20.5
2006	19.6
2007	18.7