Year years 1960 40.24757760235954 1961 40.630545367759886 1962 41.16885308301329 1963 41.29312851982853 1964 41.99125224178472 1965 41.98049507764259 1966 42.3904446955935 1967 42.94546440102468 1968 43.30486782339729 1969 43.540718049974075 1970 42.30743858689001 1971 37.759977774678546 1972 43.94637238523183 1973 44.55784935257032 1974 44.52761530923414 1975 44.552839059972875 1976 45.19074275281165 1977 45.79883566569516 1978 46.02614328970867 1979 46.49827022371203 1980 46.95139687031454 1981 47.29378635339439 1982 47.52229302078566 1983 46.80264219345937 1984 46.722285908968956 1985 47.07867770476326 1986 47.7084947584482 1987 48.22045346078462 1988 48.063124298964254 1989 49.21857108158381 1990 49.47938233795382 1991 49.23531763466743 1992 49.79528842375088 1993 50.33865976044954 1994 51.090650700568816 1995 51.57359662880115 1996 51.78720976839244 1997 52.35838778598118 1998 52.4782722155186 1999 53.80728562679256 2000 54.51015190895573 2001 54.94897970719452 2002 55.34511144324306 2003 55.87438664668234 2004 56.362970156630475 2005 56.818813522995136 2006 57.40729375681067 2007 57.78884976053766 2008 57.95995357261733 2009 58.82946729609001 2010 59.24673657038975 2011 59.88738298288758 2012 60.33517003198286 2013 60.60359450156227 2014 61.05151258402232 2015 61.38262689069334 2016 61.855365250612195 2017 62.25215789684938 2018 62.61604781219843 2019 62.87573595955123 2020 62.385980953165806 2021 61.88796600322135 2022 62.53869877398456