Year years 1960 40.133164447468886 1961 44.51634210313563 1962 50.39217541182566 1963 51.00152697722959 1964 51.63337313036675 1965 51.46999992144842 1966 52.600717855685986 1967 53.35599558339627 1968 53.89937652809353 1969 54.45094655392598 1970 55.06383602475866 1971 55.9095664581919 1972 56.57283593088269 1973 57.30304013230171 1974 57.84495750066616 1975 58.41643625781761 1976 59.074361472760835 1977 59.64988034985616 1978 60.144067995985125 1979 60.6966417316447 1980 61.1209383580652 1981 61.47988090351206 1982 61.95123340229651 1983 62.42279186067018 1984 62.92532911927254 1985 63.32659878775123 1986 63.75302431720017 1987 64.08761416001839 1988 64.33058331420851 1989 64.7159893922587 1990 64.88389854071553 1991 65.2561807859693 1992 65.6179566402224 1993 65.90909756902498 1994 66.26689331701617 1995 66.54641408817683 1996 66.86557527715968 1997 67.22938066512042 1998 67.57497527976493 1999 67.89667761660604 2000 68.20317469075805 2001 68.55218564319986 2002 68.88418071180357 2003 69.10868163852925 2004 69.29851697557007 2005 69.74180954715125 2006 70.0542229461678 2007 70.28626981648837 2008 70.49545123255093 2009 70.88377452738399 2010 71.15529970523556 2011 71.44096579654538 2012 71.71198261561436 2013 71.98420937192343 2014 72.26785022249743 2015 72.46597658952581 2016 72.58220228160816 2017 72.64969765667159 2018 73.08151049554249 2019 73.29247025166296 2020 72.40551042573075 2021 72.09202677382198 2022 72.99842646768823