Year	Cases per 100,000
1990	0.5
1991	0.6
1992	0.7
1993	0.9
1994	1.1
1995	1.3
1996	1.5
1997	1.7
1998	2
1999	2.3
2000	2.6
2001	2.8
2002	3.1
2003	3.4
2004	3.6
2005	3.8
2006	4
2007	4.2