Year years 1960 44.75757282276755 1961 46.01085717967032 1962 46.32154250059715 1963 46.90786896475521 1964 47.58556125954767 1965 48.1975181930748 1966 49.22496593823633 1967 49.699264935943006 1968 50.135277226841644 1969 50.74679270204952 1970 51.34092912053077 1971 52.03600788907809 1972 52.60734961139467 1973 53.22151330996821 1974 54.03670936596042 1975 54.6619913311596 1976 55.144926380066224 1977 56.410653022185194 1978 56.976034194738986 1979 58.16529368015021 1980 58.571006086000935 1981 58.51532629607877 1982 59.001418175798754 1983 60.489710581160224 1984 61.72761541209349 1985 62.50182378573197 1986 63.05920152772657 1987 63.75486513605023 1988 64.12067868021416 1989 65.0399400257224 1990 65.06327204704543 1991 66.20223153395962 1992 66.77198292474341 1993 67.10089979739686 1994 67.29543630643833 1995 67.60745660242813 1996 67.99366757342185 1997 68.26159417365092 1998 68.49643095507962 1999 68.91939520418148 2000 69.28217806821041 2001 69.63113154032241 2002 69.97659245243484 2003 69.8601811862713 2004 70.33843986271532 2005 70.6309307908833 2006 70.84028813735318 2007 71.18035916020979 2008 71.46639113422114 2009 71.81980690706668 2010 72.10638331940117 2011 72.37228523104382 2012 72.28467802462883 2013 72.3442426683639 2014 72.62386339011542 2015 72.88951608401229 2016 73.15252184269133 2017 73.60974285409922 2018 73.8115171255443 2019 73.95911501119359 2020 72.94976833193155 2021 72.745678008424 2022 73.21126324947248