Year years 1960 64.5582415101558 1961 64.9713325638107 1962 64.94560408245682 1963 65.09255832787815 1964 65.50319885091054 1965 65.61901002416847 1966 65.82441134942403 1967 66.10703040464352 1968 65.88354176461475 1969 66.041822246922 1970 66.33628065643035 1971 66.59056628953495 1972 66.82341491833465 1973 66.98678745182016 1974 67.37411134490505 1975 67.6134896402347 1976 67.87049660784264 1977 68.22782745098746 1978 68.37096504702417 1979 68.69824011148845 1980 68.80288039555778 1981 69.2011328549001 1982 69.56863050272959 1983 69.71802461493836 1984 70.0125192997659 1985 70.11872022457388 1986 70.45457050072585 1987 70.74323060491153 1988 70.87752784592251 1989 71.09956345779543 1990 71.20737684220428 1991 71.3993077146659 1992 71.67504839858016 1993 71.82145252746281 1994 72.10234919936012 1995 72.22292730993429 1996 72.67687451479756 1997 73.0628186752775 1998 73.30816327253973 1999 73.48595506308057 2000 73.89149352574806 2001 74.2163118854663 2002 74.42666608178739 2003 74.59018600658193 2004 75.00150532867411 2005 75.13799307558638 2006 75.43852825464448 2007 75.66170071544909 2008 75.84780445148053 2009 76.13274372342295 2010 76.33398814571034 2011 76.57179163291157 2012 76.76680171978995 2013 76.99055104886223 2014 77.25200332469083 2015 77.15212143312347 2016 77.25003655343207 2017 77.30795332160348 2018 77.37992473542846 2019 77.58129053484528 2020 76.09045741780183 2021 75.8029380186234 2022 76.96294400805455