Year Cases per 100,000 1990 5.75 1991 5.72 1992 5.68 1993 5.65 1994 5.64 1995 5.62 1996 5.59 1997 5.58 1998 5.53 1999 5.37 2000 5.22 2001 5.05 2002 4.8 2003 4.63 2004 4.42 2005 4.27 2006 4.15 2007 4 2008 3.98 2009 3.9 2010 3.85 2011 3.84 2012 3.8 2013 3.76 2014 3.71 2015 3.66 2016 3.62