Year Cases per 100,000 1953 2.5 1954 2.37 1955 2.64 1956 2.54 1957 2.92 1958 2.44 1959 2.69 1960 2.62 1961 2.93 1962 2.76 1963 2.67 1964 3.53 1965 2.58 1966 2.91 1967 4.25 1968 3.74 1969 4.88 1970 5.24 1971 4.8705 1972 5.401 1973 5.1315 1974 5.362 1975 6.5025 1976 6.263 1977 6.5035 1978 7.494 1979 7.5445 1980 8.215 1981 9.3555 1982 9.556 1983 10.2265 1984 10.687 1985 11.3075 1986 11.958 1987 13.2685 1988 13.359 1989 14.8495 1990 15.72 1991 16.63 1992 17.5 1993 18.5 1994 19.46 1995 20.36 1996 21.45 1997 22.59 1998 23.14 1999 24.3 2000 26.09 2001 27.29 2002 28.13 2003 28.78 2004 29.6 2005 30.42 2006 31 2007 31.87 2008 32.36 2009 32.87 2010 34.41 2011 34.59 2012 34.87 2013 34.8 2014 34.27 2015 33.4 2016 32.73