Year years 1960 50.74 1961 51.55 1962 52.382 1963 53.173 1964 53.714 1965 54.258 1966 54.71 1967 55.361 1968 55.835 1969 56.378 1970 56.895 1971 57.409 1972 58.069 1973 58.521 1974 59.051 1975 59.497 1976 59.965 1977 60.743 1978 61.37 1979 61.912 1980 62.504 1981 63.01 1982 63.604 1983 64.146 1984 64.706 1985 65.24 1986 65.772 1987 66.278 1988 66.794 1989 67.245 1990 67.709 1991 68.169 1992 68.486 1993 68.911 1994 69.295 1995 69.609 1996 70.141 1997 70.57 1998 71.039 1999 70.695 2000 71.861 2001 72.231 2002 72.579 2003 72.89 2004 73.24 2005 73.534 2006 73.845 2007 74.193 2008 74.45 2009 74.765 2010 75.069 2011 74.941 2012 75.678 2013 76.297 2014 76.565 2015 76.646 2016 76.66 2017 77.141 2018 77.563 2019 77.832 2020 75.85 2021 76.032 2022 78.475