Year years 1960 45.94 1961 46.484 1962 47.1 1963 47.609 1964 48.148 1965 48.782 1966 49.343 1967 50.053 1968 50.915 1969 51.816 1970 52.715 1971 53.773 1972 54.792 1973 55.932 1974 57.017 1975 58.068 1976 58.966 1977 59.947 1978 60.872 1979 61.697 1980 62.698 1981 63.472 1982 64.304 1983 65.053 1984 65.689 1985 66.33 1986 66.921 1987 67.4 1988 67.972 1989 68.491 1990 68.948 1991 69.366 1992 69.925 1993 70.303 1994 70.705 1995 71.011 1996 71.273 1997 71.483 1998 71.879 1999 72.136 2000 72.467 2001 72.974 2002 73.337 2003 73.628 2004 74.153 2005 74.588 2006 74.81 2007 75.046 2008 75.274 2009 75.431 2010 75.763 2011 76.234 2012 76.461 2013 76.626 2014 76.757 2015 76.918 2016 77.064 2017 77.16 2018 77.212 2019 77.304 2020 76.239 2021 76.936 2022 77.905