Year	Cases per 100,000
1990	1
1991	1.3
1992	1.7
1993	2.1
1994	2.6
1995	3
1996	3.5
1997	3.9
1998	4.2
1999	4.4
2000	4.6
2001	4.7
2002	4.8
2003	4.8
2004	4.7
2005	4.7
2006	4.6
2007	4.6