Year years 1960 53.41462931889417 1961 53.8831179490288 1962 54.470266685622605 1963 55.00004988968223 1964 55.1769643496463 1965 56.09117377803572 1966 56.470860943702114 1967 56.96681251552376 1968 57.31894005295565 1969 57.44837444483622 1970 57.80156911506187 1971 58.11648252940478 1972 58.31664394423881 1973 58.23422388798241 1974 58.8035592471844 1975 58.81533306291091 1976 59.32271235962696 1977 59.54244991782687 1978 59.947063671712264 1979 60.30070084285991 1980 60.451616825778395 1981 60.662981914676955 1982 60.84330421906536 1983 61.208423976608195 1984 61.615391308601374 1985 62.03484898801026 1986 62.124557092197314 1987 62.412163771194585 1988 62.73166576536528 1989 62.925726495620445 1990 63.18682114046768 1991 63.43049553508259 1992 63.662662700463365 1993 63.88373626048147 1994 64.09378700101792 1995 64.3526788945778 1996 64.5996881506545 1997 64.75638723737954 1998 64.94762379738425 1999 65.04968502064119 2000 65.05558104111994 2001 65.21961919512952 2002 65.07173857150693 2003 65.41147871596351 2004 65.61905274403233 2005 65.7840146985193 2006 65.99889054266608 2007 66.01925835964894 2008 66.159110268139 2009 66.09565935673916 2010 66.44975243774049 2011 66.57196841174624 2012 66.6918943577056 2013 66.70204350495108 2014 66.72908769513391 2015 66.62960266816836 2016 66.94670724400694 2017 67.23817113704425 2018 67.33944737632376 2019 67.43267994828675 2020 67.52190909345457 2021 67.30694863335644 2022 67.79018910256653