Year | Value | 2021 | 31.476725642269 | 2020 | 31.539813378575 | 2019 | 32.128090159961 | 2018 | 32.147721764421 | 2017 | 32.169413475521 | 2016 | 32.357852641784 | 2015 | 32.942922927775 | 2014 | 32.891420261755 | 2013 | 32.918080465342 | 2012 | 33.145904023267 | 2011 | 33.413717886573 | 2010 | 33.679108095007 | 2009 | 33.870576829859 | 2008 | 34.045079980611 | 2007 | 34.295928259816 | 2006 | 34.455889481338 | 2005 | 34.619486185167 | 2004 | 34.747939893359 | 2003 | 34.964008725157 | 2002 | 35.169655841008 | 2001 | 35.338099854581 | 2000 | 35.630150266602 | 1999 | 35.811924381968 | 1998 | 35.868880271449 | 1997 | 35.925836160931 | 1996 | 36.031265147843 | 1995 | 36.125787687833 | 1994 | 36.283325254484 | 1993 | 36.342704798837 | 1992 | 36.512360639845 | 1991 | 36.801987396995 | 1990 | 36.644449830344 | 1989 | 36.968007755696 | 1988 | 36.940135724673 | 1987 | 36.694134755211 | 1986 | 36.679592825982 | 1985 | 36.809258361609 | 1984 | 36.757149781871 | 1983 | 36.66868637906 | 1982 | 38.084100824043 | 1981 | 38.238002908386 | 1980 | 38.063499757635 | 1979 | 38.086524478914 | 1978 | 38.545807077072 | 1977 | 38.507028599128 | 1976 | 38.578526417838 | 1975 | 38.651236063984 | 1974 | 38.866941347552 | 1973 | 39.047503635482 | 1972 | 40.076345128454 | 1971 | 40.24357731459 | 1970 | 40.424139602521 | 1969 | 40.609549200194 | 1968 | 40.708919049927 | 1967 | 40.883422200679 | 1966 | 41.274842462433 | 1965 | 41.980126030053 | 1964 | 42.129180804653 | 1963 | 42.290353853611 | 1962 | 42.78962675715 | 1961 | 43.085312651478 |
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