| Year | Value | | 2021 | 48.722191579334 | | 2020 | 48.722191579334 | | 2019 | 48.722191579334 | | 2018 | 48.722191579334 | | 2017 | 48.722191579334 | | 2016 | 48.722191579334 | | 2015 | 48.722191579334 | | 2014 | 48.722191579334 | | 2013 | 48.722191579334 | | 2012 | 48.722191579334 | | 2011 | 45.22890237176 | | 2010 | 45.22890237176 | | 2009 | 45.045045045045 | | 2008 | 44.677330391616 | | 2007 | 44.309615738187 | | 2006 | 43.941901084758 | | 2005 | 43.574186431329 | | 2004 | 43.2064717779 | | 2003 | 42.838757124471 | | 2002 | 42.471042471043 | | 2001 | 42.103327817613 | | 2000 | 41.735613164185 | | 1999 | 41.367898510756 | | 1998 | 41.000183857327 | | 1997 | 40.632469203898 | | 1996 | 40.264754550469 | | 1995 | 39.89703989704 | | 1994 | 39.529325243611 | | 1993 | 39.161610590182 | | 1992 | 38.793895936753 | | 1991 | 38.426181283324 | | 1990 | 38.058466629895 | | 1989 | 37.690751976466 | | 1988 | 37.690751976466 | | 1987 | 37.139179996323 | | 1986 | 36.771465342894 | | 1985 | 36.771465342894 | | 1984 | 36.771465342894 | | 1983 | 35.852178709322 | | 1982 | 35.852178709322 | | 1981 | 35.852178709322 | | 1980 | 35.852178709322 | | 1979 | 35.852178709322 | | 1978 | 34.932892075749 | | 1977 | 33.094318808604 | | 1976 | 33.094318808604 | | 1975 | 33.094318808604 | | 1974 | 33.094318808604 | | 1973 | 33.094318808604 | | 1972 | 33.094318808604 | | 1971 | 33.094318808604 | | 1970 | 33.094318808604 | | 1969 | 33.094318808604 | | 1968 | 33.094318808604 | | 1967 | 33.094318808604 | | 1966 | 33.094318808604 | | 1965 | 33.094318808604 | | 1964 | 33.094318808604 | | 1963 | 33.094318808604 | | 1962 | 33.094318808604 | | 1961 | 33.094318808604 |
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