Year | Value | 2021 | 28.073816680641 | 2020 | 28.083024613968 | 2019 | 28.097211329315 | 2018 | 28.172669801898 | 2017 | 28.20258730489 | 2016 | 28.227140877468 | 2015 | 28.251301785688 | 2014 | 28.279990750005 | 2013 | 28.278714721404 | 2012 | 28.283052672755 | 2011 | 28.303583054917 | 2010 | 28.353812003226 | 2009 | 28.112514884087 | 2008 | 28.151178134328 | 2007 | 28.19512400125 | 2006 | 28.324479105829 | 2005 | 28.338970557203 | 2004 | 28.403160769866 | 2003 | 28.467116578607 | 2002 | 28.57228115552 | 2001 | 28.676199883257 | 2000 | 28.743083387286 | 1999 | 28.753994601335 | 1998 | 28.784962756844 | 1997 | 28.84619923776 | 1996 | 28.756075770132 | 1995 | 28.865711797303 | 1994 | 29.130745376023 | 1993 | 29.15827717972 | 1992 | 29.276017338448 | 1991 | 56.051988000637 | 1990 | 55.788124437054 | 1989 | 55.941245756253 | 1988 | 55.716649703314 | 1987 | 55.851664139473 | 1986 | 55.166898614544 | 1985 | 54.937027882212 | 1984 | 54.579758912684 | 1983 | 53.912302930852 | 1982 | 54.241876631424 | 1981 | 55.228520587971 | 1980 | 55.285988271054 | 1979 | 55.549785707857 | 1978 | 55.006958436325 | 1977 | 55.018728925631 | 1976 | 54.926642156354 | 1975 | 54.813783935359 | 1974 | 55.164821469372 | 1973 | 55.490933261326 | 1972 | 55.623178170589 | 1971 | 55.366996932749 | 1970 | 55.315068303457 | 1969 | 55.684800144015 | 1968 | 55.024267979422 | 1967 | 54.742468617798 | 1966 | 54.911409758428 | 1965 | 54.741776236075 | 1964 | 54.813091553635 | 1963 | 54.839402059143 | 1962 | 54.362351051382 | 1961 | 54.24464615832 |
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