Year	Cases per 100,000
1990	0.1
1991	0.3
1992	0.7
1993	1
1994	1.4
1995	1.8
1996	2.1
1997	2.3
1998	2.6
1999	2.9
2000	3.2
2001	3.5
2002	3.6
2003	3.6
2004	3.5
2005	3.3
2006	3.1
2007	2.8