Year | Value | 2021 | 36.847182912799 | 2020 | 36.815108868271 | 2019 | 36.756401123594 | 2018 | 36.722624374163 | 2017 | 36.644995187945 | 2016 | 36.526834685029 | 2015 | 36.411833916973 | 2014 | 36.337058583485 | 2013 | 36.223204040317 | 2012 | 36.052973209191 | 2011 | 36.006308377448 | 2010 | 35.827128660569 | 2009 | 35.628072782319 | 2008 | 35.491818452634 | 2007 | 35.490588648152 | 2006 | 35.325990172793 | 2005 | 35.184070238147 | 2004 | 34.82193356389 | 2003 | 34.994512218532 | 2002 | 34.736511434853 | 2001 | 34.644375536852 | 2000 | 34.499669750838 | 1999 | 34.394470040604 | 1998 | 34.311915314849 | 1997 | 34.256827090458 | 1996 | 34.158541122446 | 1995 | 34.004498852198 | 1994 | 33.764354442003 | 1993 | 33.554563711599 | 1992 | 34.209820771069 | 1991 | 32.919820809511 | 1990 | 32.791449708532 | 1989 | 32.665007152752 | 1988 | 32.588141912106 | 1987 | 32.395545264012 | 1986 | 32.30317436102 | 1985 | 32.097367296651 | 1984 | 31.955776116802 | 1983 | 31.94914540593 | 1982 | 31.904005566533 | 1981 | 31.875187476974 | 1980 | 31.878604843347 | 1979 | 31.804544903455 | 1978 | 31.743287336092 | 1977 | 31.709368699709 | 1976 | 31.683202894499 | 1975 | 31.616197010865 | 1974 | 31.587805575814 | 1973 | 31.585778949994 | 1972 | 31.56297023529 | 1971 | 31.475805446764 | 1970 | 31.422047876777 | 1969 | 31.423781991938 | 1968 | 31.348041962119 | 1967 | 31.271485878106 | 1966 | 31.237517622308 | 1965 | 31.222777643441 | 1964 | 31.193807719577 | 1963 | 31.158717389263 | 1962 | 31.102205636374 | 1961 | 31.032228989295 |
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