Year | Value | 2021 | 34.670547931837 | 2020 | 34.669496333926 | 2019 | 34.599014272074 | 2018 | 34.629036535686 | 2017 | 34.653463084992 | 2016 | 34.665203780007 | 2015 | 34.686801178871 | 2014 | 34.680426012889 | 2013 | 34.753859257321 | 2012 | 34.754688603894 | 2011 | 34.746800536581 | 2010 | 34.787394940429 | 2009 | 34.643762748122 | 2008 | 34.679794044266 | 2007 | 34.786122702925 | 2006 | 34.762171115166 | 2005 | 34.753909514127 | 2004 | 34.739010319346 | 2003 | 34.713118609271 | 2002 | 34.692477347517 | 2001 | 34.671032034111 | 2000 | 34.699539785815 | 1999 | 34.702943584367 | 1998 | 34.667094330733 | 1997 | 34.642107194507 | 1996 | 34.590965021032 | 1995 | 34.605972798817 | 1994 | 34.725906706528 | 1993 | 34.67948620807 | 1992 | 34.647028144689 | 1991 | 40.129486031352 | 1990 | 40.039698343819 | 1989 | 39.767162985895 | 1988 | 39.559809125877 | 1987 | 39.373456265316 | 1986 | 39.091945395679 | 1985 | 38.851935406873 | 1984 | 38.326695443461 | 1983 | 37.899961457334 | 1982 | 37.460431709573 | 1981 | 37.130783151233 | 1980 | 36.886560307742 | 1979 | 36.578362519001 | 1978 | 36.252614066257 | 1977 | 35.881119377621 | 1976 | 35.513145707134 | 1975 | 35.166737146343 | 1974 | 34.91225005016 | 1973 | 34.593197452446 | 1972 | 34.279899426215 | 1971 | 33.95371351577 | 1970 | 33.663457768696 | 1969 | 33.410063893527 | 1968 | 33.176198709907 | 1967 | 32.950434662786 | 1966 | 32.76508895049 | 1965 | 32.563538082433 | 1964 | 32.375979274098 | 1963 | 32.208720007749 | 1962 | 32.019010659299 | 1961 | 31.843646220584 |
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