Year Cases per 100,000 1990 4.27 1991 4.44 1992 4.63 1993 4.82 1994 5.03 1995 5.25 1996 5.2 1997 5.17 1998 5.13 1999 5.1 2000 5.07 2001 4.89 2002 4.72 2003 4.56 2004 4.4 2005 4.25 2006 4.1 2007 3.96 2008 3.82 2009 3.69 2010 3.56 2011 3.58 2012 3.59 2013 3.61 2014 3.63 2015 3.64 2016 3.66