Year	Cases per 100,000
1990	0.5
1991	1.2
1992	2.8
1993	5.9
1994	10
1995	13.8
1996	16.4
1997	17.7
1998	18.2
1999	18.3
2000	18.1
2001	17.8
2002	17.5
2003	17.1
2004	16.7
2005	16.4
2006	16.1
2007	15.8