Year	Cases per 100,000
1990	1.8
1991	2
1992	2.3
1993	2.7
1994	3
1995	3.3
1996	3.6
1997	3.8
1998	4.1
1999	4.3
2000	4.4
2001	4.5
2002	4.6
2003	4.6
2004	4.7
2005	4.6
2006	4.6
2007	4.6