Year Cases per 100,000 1990 33.6 1991 33.76 1992 33.95 1993 34.15 1994 34.34 1995 34.56 1996 34.28 1997 34.02 1998 33.76 1999 33.51 2000 33.3 2001 32.6 2002 31.96 2003 31.33 2004 30.72 2005 30.16 2006 29.84 2007 29.51 2008 29.2 2009 28.89 2010 28.61 2011 28.45 2012 28.3 2013 28.16 2014 28.01 2015 27.87 2016 27.75