Year	Cases per 100,000
1990	7.6
1991	8.3
1992	8.3
1993	7.9
1994	7.4
1995	7
1996	6.5
1997	6.1
1998	5.7
1999	5.3
2000	4.9
2001	4.6
2002	4.3
2003	4
2004	3.7
2005	3.5
2006	3.3
2007	3.1