Year years 1960 44.972898651669894 1961 45.67640149749665 1962 46.12257584528735 1963 46.97247170646677 1964 47.89575845641874 1965 48.2321074069176 1966 48.45707277658731 1967 48.912911191235914 1968 49.44511952130966 1969 49.82223582359719 1970 50.35134318137286 1971 51.29642393168458 1972 51.86445798833013 1973 52.53968339398722 1974 53.19444453097972 1975 53.70985801760173 1976 54.04753359018671 1977 55.361470341669744 1978 56.112173493827555 1979 56.82629234989416 1980 57.30237239117356 1981 57.692929471800205 1982 58.0547979155265 1983 58.787368432600054 1984 59.47897587708015 1985 60.21573678951583 1986 61.22126232817299 1987 61.16971172930249 1988 60.60902529817948 1989 62.48114365681431 1990 62.92796703295272 1991 63.1796143554706 1992 63.47441021041171 1993 64.45832147259863 1994 65.49672687220142 1995 65.34978333037773 1996 65.71840452297911 1997 65.99441940020867 1998 65.8077067945681 1999 66.87672731959469 2000 67.29733125523734 2001 67.6316805976471 2002 67.93557016325819 2003 67.85900283350051 2004 67.89591204418906 2005 68.16268217967931 2006 68.56724961180083 2007 68.92868036602279 2008 69.28642729404757 2009 69.81263770437707 2010 70.04125357145433 2011 70.26151981300228 2012 70.1804605984523 2013 70.19651371013074 2014 70.49262887112948 2015 70.75822222882107 2016 70.94306227819227 2017 71.4295960025113 2018 71.63301665494629 2019 71.84462602504462 2020 70.92335958723314 2021 70.81448302106303 2022 71.22727445474376