Year Cases per 100,000 1990 6.2 1991 8.7 1992 12 1993 16.2 1994 21 1995 26.3 1996 31.8 1997 37.1 1998 41.8 1999 45.7 2000 48.8 2001 51.1 2002 52.6 2003 53.7 2004 54.4 2005 54.9 2006 55.2 2007 55.4