Year | Value | 2022 | 51.750790413134 | 2021 | 51.735449781456 | 2020 | 51.723073981016 | 2019 | 51.714348307314 | 2018 | 51.703551594559 | 2017 | 51.691876708053 | 2016 | 51.680287791088 | 2015 | 51.66968647709 | 2014 | 51.659762969343 | 2013 | 51.647032673927 | 2012 | 51.630979898222 | 2011 | 51.615596011893 | 2010 | 51.603008854026 | 2009 | 51.588771126916 | 2008 | 51.570968020438 | 2007 | 51.554915455791 | 2006 | 51.54337301 | 2005 | 51.53925511943 | 2004 | 51.541038854165 | 2003 | 51.54887296553 | 2002 | 51.566169364981 | 2001 | 51.583762568668 | 2000 | 51.586820372912 | 1999 | 51.576497924677 | 1998 | 51.564011237631 | 1997 | 51.551048225829 | 1996 | 51.537453653369 | 1995 | 51.524695241595 | 1994 | 51.51281819296 | 1993 | 51.503277843789 | 1992 | 51.504597085423 | 1991 | 51.528485458991 | 1990 | 51.563939223279 | 1989 | 51.638342636658 | 1988 | 51.707315457855 | 1987 | 51.716362201076 | 1986 | 51.718323494289 | 1985 | 51.715019788514 | 1984 | 51.704669042698 | 1983 | 51.68790564184 | 1982 | 51.664810247434 | 1981 | 51.622148807872 | 1980 | 51.566505531796 | 1979 | 51.542826223659 | 1978 | 51.536427454531 | 1977 | 51.533890719127 | 1976 | 51.548611727136 | 1975 | 51.56883861223 | 1974 | 51.596005604106 | 1973 | 51.627070811887 | 1972 | 51.661358214362 | 1971 | 51.698273476663 | 1970 | 51.737186649648 | 1969 | 51.777710160313 | 1968 | 51.818361740922 | 1967 | 51.858200481053 | 1966 | 51.896659543759 | 1965 | 51.934602750928 | 1964 | 51.952327997334 | 1963 | 51.941156405115 | 1962 | 51.914442301176 | 1961 | 51.870394264279 | 1960 | 51.80919073979 |
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