Year years 1960 52.66 1961 53.183 1962 53.71 1963 54.209 1964 54.648 1965 55.084 1966 55.473 1967 55.868 1968 56.31 1969 56.748 1970 57.171 1971 57.586 1972 58.032 1973 58.472 1974 58.881 1975 59.353 1976 59.792 1977 60.24 1978 60.72 1979 61.253 1980 61.781 1981 62.333 1982 62.856 1983 63.331 1984 63.773 1985 64.198 1986 64.64 1987 65.08 1988 65.454 1989 65.868 1990 65.985 1991 66.31 1992 66.708 1993 67.109 1994 67.568 1995 67.919 1996 68.409 1997 68.813 1998 69.189 1999 69.524 2000 69.737 2001 70.195 2002 70.41 2003 70.72 2004 71.131 2005 71.753 2006 72.037 2007 72.365 2008 72.715 2009 72.948 2010 73.182 2011 73.343 2012 73.552 2013 73.918 2014 74.306 2015 74.332 2016 74.442 2017 74.827 2018 75.109 2019 75.338 2020 74.009 2021 72.75 2022 73.425