Year	Cases per 100,000
1990	0.4
1991	0.6
1992	0.9
1993	1.3
1994	1.8
1995	2.4
1996	2.9
1997	3.4
1998	3.7
1999	4
2000	4.1
2001	4.2
2002	4.2
2003	4.2
2004	4.2
2005	4.2
2006	4.2
2007	4.2