| Year | Value | | 2022 | 0.99629546974113 | | 2021 | 1.4068259065087 | | 2020 | 1.2972400391073 | | 2019 | 1.1313313248367 | | 2018 | 1.1842471769674 | | 2017 | 1.1679608335523 | | 2016 | 1.0455851467389 | | 2015 | 1.0884630395817 | | 2014 | 1.0431270655947 | | 2013 | 1.1895017289376 | | 2012 | 1.1067041897598 | | 2011 | 1.153414552057 | | 2010 | 1.1701322006025 | | 2009 | 1.2023233937147 | | 2008 | 1.2503290879835 | | 2007 | 1.2914259163093 | | 2006 | 1.2590953916093 | | 2005 | 1.2778839364326 | | 2004 | 1.3606265097066 | | 2003 | 1.5508448291791 | | 2002 | 1.4738901879337 | | 2001 | 1.4713788325538 | | 2000 | 1.608226620868 | | 1999 | 1.6157758461254 | | 1998 | 1.6972933797532 | | 1997 | 1.9144613761672 | | 1996 | 2.2684076761575 | | 1995 | 2.2941315354548 | | 1994 | 2.172446586687 | | 1993 | 2.1575356401666 | | 1992 | 2.0364615703335 | | 1991 | 2.0107210679402 | | 1990 | 2.1472466674093 | | 1989 | 2.2429233967695 | | 1988 | 2.4588892142215 | | 1987 | 1.9652471424973 | | 1986 | 1.9880536125751 | | 1985 | 1.9825733585366 | | 1984 | 1.6347589331167 | | 1983 | 2.4092533536362 | | 1982 | 2.5972879496306 | | 1981 | 2.7557209619455 | | 1980 | 2.709754706686 | | 1979 | 2.9649310710986 | | 1978 | 2.581767218817 | | 1977 | 3.6213089881084 | | 1976 | 3.9313383405287 | | 1974 | 3.5580392590433 | | 1973 | 2.8138049279611 | | 1972 | 2.3361569326795 | | 1971 | 2.0699906226931 | | 1970 | 2.1567565020731 | | 1969 | 2.0908884859474 | | 1968 | 1.8674717544897 | | 1967 | 1.7399393605292 | | 1966 | 1.6517270690055 | | 1965 | 1.5491998638066 | | 1964 | 1.7049424698374 | | 1963 | 1.8558622078969 | | 1962 | 1.8088157817713 | | 1961 | 1.7029080429657 | | 1960 | 1.7784589065507 |
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