| Year | Value | | 2021 | 66.454329817597 | | 2020 | 70.143086258256 | | 2019 | 60.62688647761 | | 2018 | 56.361982719418 | | 2017 | 63.678938802293 | | 2016 | 64.138193651123 | | 2015 | 60.70188307676 | | 2014 | 50.776874992986 | | 2013 | 48.126106117916 | | 2012 | 46.418338108883 | | 2011 | 46.145688607884 | | 2010 | 45.727954381753 | | 2009 | 55.803702185102 | | 2008 | 42.223153741053 | | 2007 | 49.434359345944 | | 2006 | 48.340285874933 | | 2005 | 51.356208267913 | | 2004 | 59.590803381549 | | 2003 | 59.839990109352 | | 2002 | 59.811549026967 | | 2001 | 60.421699951314 | | 2000 | 56.846373474284 | | 1999 | 67.682267238938 | | 1998 | 73.762547744824 | | 1997 | 70.908941620823 | | 1996 | 72.260524658257 | | 1995 | 76.54086035688 | | 1994 | 76.043323334608 | | 1993 | 77.468981597135 | | 1992 | 74.477328265001 | | 1991 | 76.655659512016 | | 1990 | 68.020654810924 | | 1989 | 62.726165501165 | | 1988 | 66.233524577454 | | 1987 | 61.373771771118 | | 1986 | 69.664361094315 | | 1985 | 59.715271266972 | | 1984 | 57.32055531852 | | 1983 | 57.932773383436 | | 1982 | 58.009501877462 | | 1981 | 50.404819909671 | | 1980 | 52.707995740768 | | 1979 | 53.640946103141 | | 1978 | 61.616475265032 | | 1977 | 54.362055939791 | | 1976 | 47.777914734819 | | 1975 | 47.514519126556 | | 1974 | 43.412489006156 | | 1973 | 61.157024793388 | | 1972 | 54.545454545454 | | 1971 | 37.8896882494 | | 1970 | 32.209737827715 | | 1969 | 28 | | 1968 | 32.020330368488 | | 1967 | 57.474226804124 |
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