| Year | Value | | 2022 | 1.1797370813359 | | 2021 | 1.0503440493909 | | 2020 | 1.0145135239111 | | 2019 | 0.88848729225209 | | 2018 | 0.89135808480281 | | 2017 | 0.88356344600305 | | 2016 | 0.89470623618152 | | 2015 | 0.90928420206892 | | 2014 | 0.97095979114811 | | 2013 | 1.0089594787212 | | 2012 | 1.0417564900031 | | 2011 | 1.0522177697133 | | 2010 | 1.0904882165313 | | 2009 | 1.1677684366565 | | 2008 | 1.221914516589 | | 2007 | 1.0980187643928 | | 2006 | 1.0561230687849 | | 2005 | 1.0966411815857 | | 2004 | 1.1492721388045 | | 2003 | 1.2149881561653 | | 2002 | 1.2157122077646 | | 2001 | 1.2765041664723 | | 2000 | 1.3412102764288 | | 1999 | 1.3858355592209 | | 1998 | 1.46391926511 | | 1997 | 1.4769757958789 | | 1996 | 1.5401026514345 | | 1995 | 1.5657521514464 | | 1994 | 1.6771431501231 | | 1993 | 1.7359658934332 | | 1992 | 1.8323325300937 | | 1991 | 2.2876928471248 | | 1990 | 2.3554404589172 | | 1989 | 2.4608543235523 | | 1988 | 2.6287484161622 | | 1987 | 2.901794792616 | | 1986 | 2.9537726239912 | | 1985 | 2.9312338541026 | | 1984 | 3.0079024492359 | | 1983 | 3.1914131704927 | | 1982 | 3.2699445914241 | | 1981 | 3.3660494360659 | | 1980 | 3.2501953855041 | | 1979 | 3.2613450175337 | | 1978 | 3.2615220612197 | | 1977 | 3.1432486470937 | | 1976 | 3.0933695342402 | | 1975 | 3.0650345394077 | | 1974 | 2.7614161880379 | | 1973 | 2.8353111327891 | | 1972 | 2.8807600412529 | | 1971 | 2.8989259188945 | | 1970 | 2.9186400967401 | | 1969 | 2.9318149964962 | | 1968 | 3.1150900112757 | | 1967 | 3.1345816242481 | | 1966 | 3.1125860285989 | | 1965 | 2.9730636020905 | | 1964 | 3.2134716593383 | | 1963 | 3.2166309632907 | | 1962 | 3.2847521670087 | | 1961 | 3.2590700737973 | | 1960 | 3.3973478671359 |
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