Year | Value | 2022 | 49.722721584808 | 2021 | 49.712034949842 | 2020 | 49.693998687151 | 2019 | 49.667863911357 | 2018 | 49.63177483668 | 2017 | 49.587350181292 | 2016 | 49.527955766567 | 2015 | 49.457269662492 | 2014 | 49.416229325098 | 2013 | 49.406520675525 | 2012 | 49.396942019589 | 2011 | 49.3864815739 | 2010 | 49.374842217688 | 2009 | 49.364277301916 | 2008 | 49.355110825572 | 2007 | 49.346342292849 | 2006 | 49.339224900723 | 2005 | 49.333355252703 | 2004 | 49.328025593397 | 2003 | 49.324529927941 | 2002 | 49.323485099524 | 2001 | 49.323247436499 | 2000 | 49.320115504087 | 1999 | 49.314676536566 | 1998 | 49.310075996906 | 1997 | 49.304482461645 | 1996 | 49.297926970798 | 1995 | 49.29232377921 | 1994 | 49.288984461146 | 1993 | 49.285150920847 | 1992 | 49.276439035367 | 1991 | 49.26596513061 | 1990 | 49.257509785739 | 1989 | 49.251184153223 | 1988 | 49.240130837372 | 1987 | 49.221746040017 | 1986 | 49.205876718206 | 1985 | 49.192812879517 | 1984 | 49.17867110951 | 1983 | 49.161017994787 | 1982 | 49.142698561511 | 1981 | 49.125770830683 | 1980 | 49.137286395301 | 1979 | 49.143630653063 | 1978 | 49.103518323908 | 1977 | 49.063609117649 | 1976 | 49.038165236523 | 1975 | 49.02058331631 | 1974 | 49.00592452187 | 1973 | 48.992601173371 | 1972 | 48.978212880319 | 1971 | 48.952635509121 | 1970 | 48.925097214133 | 1969 | 48.904095007356 | 1968 | 48.879659710973 | 1967 | 48.852867846902 | 1966 | 48.829907722022 | 1965 | 48.811013136165 | 1964 | 48.79078360042 | 1963 | 48.770593831952 | 1962 | 48.751830626685 | 1961 | 48.72825434485 | 1960 | 48.696883123183 |
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