Year years 1960 44.81706734663071 1961 47.70234302100125 1962 51.509613710021625 1963 51.969795470539644 1964 52.534965917531736 1965 52.47236050732822 1966 53.14301034173887 1967 53.718549093046924 1968 54.46891073400013 1969 54.97350015882083 1970 55.280989152241155 1971 55.62075178367897 1972 56.60343402263269 1973 57.30379338239631 1974 57.898905659459345 1975 58.539711174277244 1976 59.14618443057601 1977 59.85370581575232 1978 60.43684828891796 1979 61.02608453513295 1980 61.57798375388417 1981 62.09853321021385 1982 62.57249897878976 1983 63.072387503866025 1984 63.493576499554166 1985 63.862314914280994 1986 64.28649934090545 1987 64.65121359462324 1988 64.9800837833457 1989 65.31233049170223 1990 65.56348087560872 1991 65.69386890462313 1992 66.13429587461306 1993 66.44617283141305 1994 66.64855862416448 1995 66.96790727867679 1996 67.19039522985854 1997 67.56424822472157 1998 67.98454016266618 1999 68.26613324431035 2000 68.64137787501987 2001 69.16401099116828 2002 69.51001071894342 2003 69.837931128106 2004 70.05991626245559 2005 70.50847553229272 2006 70.90206742604224 2007 71.18110125228944 2008 71.3239870396908 2009 71.76284455386174 2010 72.06592249874092 2011 72.42832602763731 2012 72.79349665517252 2013 73.12919743681917 2014 73.42266412151423 2015 73.68691790711372 2016 73.97035648651395 2017 74.24734869904339 2018 74.48521971187964 2019 74.68713096974585 2020 74.15308040424411 2021 73.06455410336036 2022 73.68898265017717