Year | Value | 2021 | 18.451116113694 | 2020 | 18.451116113694 | 2019 | 18.451116113694 | 2018 | 18.153591388946 | 2017 | 18.153591388946 | 2016 | 18.153591388946 | 2015 | 18.153591388946 | 2014 | 16.559718484786 | 2013 | 16.559718484786 | 2012 | 16.559718484786 | 2011 | 16.559718484786 | 2010 | 16.559718484786 | 2009 | 16.559718484786 | 2008 | 16.559718484786 | 2007 | 16.973711446905 | 2006 | 16.973711446905 | 2005 | 16.973711446905 | 2004 | 16.973711446905 | 2003 | 16.973711446905 | 2002 | 18.588283999172 | 2001 | 18.588283999172 | 2000 | 18.588283999172 | 1999 | 17.594700890085 | 1998 | 18.008693852205 | 1997 | 17.801697371145 | 1996 | 19.354170979093 | 1995 | 19.250672738563 | 1994 | 18.629683295384 | 1993 | 18.629683295384 | 1992 | 18.629683295384 | 1991 | 18.629683295384 | 1990 | 18.629683295384 | 1989 | 20.596149865452 | 1988 | 20.513351273028 | 1987 | 20.513351273028 | 1986 | 22.252121713931 | 1985 | 22.252121713931 | 1984 | 22.252121713931 | 1983 | 22.252121713931 | 1982 | 22.252121713931 | 1981 | 22.252121713931 | 1980 | 22.148623473401 | 1979 | 21.527634030221 | 1978 | 21.010142827572 | 1977 | 20.492651624922 | 1976 | 19.871662181743 | 1975 | 18.940178016974 | 1974 | 18.319188573794 | 1973 | 17.905195611675 | 1972 | 17.594700890085 | 1971 | 17.097909335541 | 1970 | 16.973711446905 | 1969 | 16.870213206375 | 1968 | 16.145725522666 | 1967 | 16.145725522666 | 1966 | 15.938729041606 | 1965 | 15.731732560547 | 1964 | 15.524736079487 | 1963 | 15.317739598427 | 1962 | 15.110743117367 | 1961 | 14.903746636307 |
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