Year Cases per 100,000 1958 13.62 1959 13.37 1960 17.64 1961 15.27 1962 19.05 1963 14.68 1964 19.85 1965 13.29 1966 17.43 1967 19.42 1968 18.65 1969 19.08 1970 31.91 1971 23.2595 1972 13.459 1973 24.0885 1974 28.928 1975 23.5075 1976 16.547 1977 16.7065 1978 19.766 1979 25.2655 1980 22.145 1981 17.2345 1982 23.634 1983 16.8335 1984 20.953 1985 22.0225 1986 29.112 1987 21.4915 1988 23.081 1989 26.4305 1990 28.06 1991 28.49 1992 28.93 1993 29.38 1994 29.85 1995 30.33 1996 30.09 1997 29.86 1998 29.64 1999 29.43 2000 29.23 2001 28.82 2002 28.41 2003 28.01 2004 27.63 2005 27.25 2006 26.88 2007 26.51 2008 26.15 2009 25.8 2010 25.46 2011 25.82 2012 26.2 2013 26.58 2014 26.97 2015 27.36 2016 27.77