Year years 1960 46.87924373002273 1961 47.36552010069314 1962 47.78955193594714 1963 48.187870192688365 1964 48.67069859753771 1965 47.67966965957857 1966 48.66999299279224 1967 49.351341735587646 1968 50.39951896113923 1969 50.82211653786133 1970 50.76912136670321 1971 50.17385023376906 1972 52.00236801328244 1973 52.46361125010737 1974 52.92345177697767 1975 53.34744147268391 1976 53.884096032352986 1977 54.48752497735027 1978 54.979059155929534 1979 55.566752730975075 1980 56.11721526462516 1981 56.552845776686496 1982 57.04267189772011 1983 57.47965669108171 1984 58.05158193410242 1985 58.56658362740718 1986 59.0327601714472 1987 59.62241645794228 1988 60.0273415491619 1989 60.4662865938715 1990 60.827546768003224 1991 61.13543152097143 1992 61.620556411047566 1993 61.90135379122169 1994 62.157122558846964 1995 62.567320578379544 1996 62.87675609854077 1997 63.28436259172625 1998 63.710093816218645 1999 64.14361299881068 2000 64.49925708264554 2001 64.81635498567248 2002 65.22265490825167 2003 65.5196872923742 2004 65.74290199128544 2005 66.19150348399546 2006 66.59202958293525 2007 66.88471173174285 2008 67.07969004891606 2009 67.52799847782806 2010 67.86597309302013 2011 68.29176977443531 2012 68.67255327145207 2013 69.06532039554399 2014 69.48499150776087 2015 69.87120791586221 2016 70.21638780904509 2017 70.53844903119081 2018 70.79482502646407 2019 71.01473888400355 2020 70.02869341387866 2021 68.46604059199917 2022 69.3164374718329