Year | Value | 2021 | 39.434768320736 | 2020 | 39.434768320736 | 2019 | 39.524102747353 | 2018 | 38.734450226367 | 2017 | 38.827962718927 | 2016 | 38.840794289489 | 2015 | 38.763430052045 | 2014 | 34.699126594356 | 2013 | 34.67267044513 | 2012 | 34.433112037696 | 2011 | 34.373284304337 | 2010 | 34.345056081508 | 2009 | 32.906810929716 | 2008 | 32.739967774112 | 2007 | 32.194344729618 | 2006 | 32.219185089276 | 2005 | 32.138461882706 | 2004 | 31.59157609572 | 2003 | 30.757570871094 | 2002 | 30.445982933505 | 2001 | 30.483139927352 | 2000 | 28.226065710795 | 1999 | 25.847184245292 | 1998 | 24.747304064641 | 1997 | 24.099050662079 | 1996 | 23.601339518879 | 1995 | 21.748748041415 | 1994 | 21.936157792866 | 1993 | 21.773326369474 | 1992 | 21.582844327015 | 1991 | 20.741036590986 | 1990 | 20.664229315801 | 1989 | 20.630434114719 | 1988 | 20.615072659682 | 1987 | 20.615072659682 | 1986 | 20.661157024793 | 1985 | 20.737964299979 | 1984 | 21.229530861163 | 1983 | 21.204952533104 | 1982 | 21.149651294971 | 1981 | 21.125072966911 | 1980 | 21.069771728778 | 1979 | 21.045193400719 | 1978 | 21.002181326615 | 1977 | 20.928446342438 | 1976 | 20.651940151771 | 1975 | 20.006759040216 | 1974 | 19.991397585179 | 1973 | 19.914590309994 | 1972 | 19.807060124735 | 1971 | 19.73025284955 | 1970 | 19.714891394513 | 1969 | 19.607361209254 | 1968 | 19.561276844143 | 1967 | 19.484469568958 | 1966 | 19.407662293772 | 1965 | 19.392300838735 | 1964 | 19.376939383698 | 1963 | 19.361577928661 | 1962 | 19.346216473624 | 1961 | 19.330855018587 |
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