Year years 1960 43.83422493013547 1961 48.51571367659733 1962 54.787717060100675 1963 55.26823094743047 1964 55.91066965214363 1965 56.39295529065512 1966 56.903636670172425 1967 57.323129418467445 1968 57.689924176725874 1969 58.139730433528506 1970 58.889352803374706 1971 59.599334311384226 1972 60.09112562400116 1973 60.902085822501796 1974 61.45278215379651 1975 62.16121922417397 1976 62.78257169568845 1977 63.381863878113926 1978 63.9115684791393 1979 64.40222845369539 1980 64.87618800641182 1981 65.38777445407929 1982 65.82519581282344 1983 66.20344986420115 1984 66.51888275789541 1985 66.85631788138843 1986 67.34111137778021 1987 67.65187018527067 1988 67.88066295855423 1989 68.11514463938094 1990 68.25341754738663 1991 68.40002886848912 1992 68.70163386813775 1993 68.93831635238737 1994 69.14343688101522 1995 69.40908093277602 1996 69.75904796623234 1997 70.18327906479124 1998 70.61190492063999 1999 70.76304300160152 2000 71.07867528598503 2001 71.62407221684288 2002 71.92144525319723 2003 72.33391383401347 2004 72.63780546281525 2005 73.03141242874901 2006 73.45089488568321 2007 73.7432702982702 2008 73.92101891660712 2009 74.33245812651427 2010 74.61509393454457 2011 74.94891714972263 2012 75.22591829111558 2013 75.52036230623757 2014 75.78971453892483 2015 76.01184827489512 2016 76.25676920744704 2017 76.39813914455479 2018 76.76900002214661 2019 76.99116877036003 2020 76.72040172968423 2021 76.36781722560913 2022 77.09815467637651