Year | Value | 2022 | 14.869741729604 | 2021 | 16.340361162952 | 2020 | 14.4751390056 | 2019 | 13.216023152562 | 2018 | 13.23023652688 | 2017 | 14.243708084735 | 2016 | 14.287918390863 | 2015 | 14.288975935155 | 2014 | 13.68177341644 | 2013 | 13.837843683825 | 2012 | 13.497377204014 | 2011 | 16.10205685689 | 2010 | 17.14240591184 | 2009 | 17.377436226823 | 2008 | 16.323646336866 | 2007 | 17.007036591815 | 2006 | 18.106624401938 | 2005 | 17.698097525412 | 2004 | 16.981241346682 | 2003 | 18.385602193613 | 2002 | 17.946274668955 | 2001 | 14.75987098618 | 2000 | 15.10713113849 | 1999 | 14.413492540398 | 1998 | 14.770726942676 | 1997 | 14.872100567823 | 1996 | 15.667634046853 | 1995 | 16.722924375095 | 1994 | 15.371343978797 | 1993 | 15.818170849511 | 1992 | 14.765270875913 | 1991 | 14.919015349846 | 1990 | 14.533965260908 | 1989 | 18.988757241899 | 1988 | 18.2771443405 | 1987 | 18.315602968758 | 1986 | 20.000175752296 | 1985 | 21.259353207853 | 1984 | 21.193888547435 | 1983 | 22.430808468658 | 1982 | 23.318357636189 | 1981 | 26.318410076729 | 1980 | 30.137337966637 | 1979 | 27.788183824225 | 1978 | 26.497459663283 | 1977 | 25.997057031404 | 1976 | 25.752452267788 | 1975 | 26.534419897336 | 1974 | 32.25817340344 | 1973 | 30.429984136663 | 1972 | 27.082294873289 | 1971 | 26.355786979003 | 1970 | 27.817366059659 | 1969 | 29.763722282867 | 1968 | 30.461085677024 | 1967 | 32.085656136692 | 1966 | 30.351689488783 | 1965 | 30.273165506224 | 1964 | 29.461358313869 | 1963 | 30.878369663382 | 1962 | 29.215406562094 | 1961 | 28.573596358131 | 1960 | 27.812449992005 |
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