Year years 1960 64.87610928210144 1961 65.19862746767326 1962 65.34632666760065 1963 65.8331122064259 1964 66.22287589199642 1965 66.32993146901593 1966 66.5108649796729 1967 66.74204068566354 1968 66.98840164874241 1969 67.09581327869714 1970 67.2626168637237 1971 67.56168815898546 1972 67.82558742984187 1973 68.05458807022232 1974 68.33462878498068 1975 68.61599407338781 1976 68.73933153043004 1977 69.00626852116282 1978 69.21210324255745 1979 69.34349207974068 1980 69.81411498211607 1981 70.06231833274114 1982 70.32941725766767 1983 70.5214747314393 1984 70.68127706650526 1985 70.85486223846841 1986 71.43294896512015 1987 71.72931556128896 1988 71.61266156774033 1989 72.2328088813128 1990 72.28509401840242 1991 72.14603538169243 1992 71.87289390307508 1993 71.61395242052332 1994 71.72351065255717 1995 71.69341415394891 1996 71.93250258883916 1997 72.21465767631071 1998 72.59566137154964 1999 72.49155542982624 2000 73.04911333155849 2001 73.3111835843296 2002 73.60056318467564 2003 73.85725478430604 2004 74.12484224220849 2005 74.19731676473619 2006 74.46363343826364 2007 74.75827222671401 2008 74.97923244254117 2009 75.36529796298773 2010 75.64090272774496 2011 75.81530246299815 2012 76.22802043300403 2013 76.6164192208087 2014 76.84289207410491 2015 76.99313248554171 2016 77.20278913798866 2017 77.47861462326904 2018 77.66800734842637 2019 77.87160635231312 2020 76.30887835351845 2021 76.07421513341396 2022 77.571300031632