| Year | Value | | 2022 | 0.71074564290373 | | 2021 | 0.72282250547578 | | 2020 | 0.83517614833256 | | 2019 | 1.0995932626289 | | 2018 | 1.307882209108 | | 2017 | 1.4288255268814 | | 2016 | 1.8358079171407 | | 2015 | 2.2617849255828 | | 2014 | 1.897214219374 | | 2013 | 1.4565059032144 | | 2012 | 1.2774254084696 | | 2011 | 1.2775500339358 | | 2010 | 1.4044242809357 | | 2009 | 1.3604702660445 | | 2008 | 1.3718850263899 | | 2007 | 1.4536370817991 | | 2006 | 1.5455966097725 | | 2005 | 1.6100400109898 | | 2004 | 1.6158639463862 | | 2003 | 0.9278209306692 | | 2002 | 0.97352473440778 | | 2001 | 1.7100319119575 | | 2000 | 1.6453919487085 | | 1999 | 1.5841418775921 | | 1998 | 1.5577141737463 | | 1997 | 1.4219497200906 | | 1996 | 1.3131131986258 | | 1995 | 1.3397389693831 | | 1994 | 0.38469520003908 | | 1993 | 0.64370610937098 | | 1992 | 2.3537195714124 | | 1991 | 3.8626121294166 | | 1990 | 3.9276340406387 | | 1989 | 2.8990631310269 | | 1988 | 3.0598132400628 | | 1987 | 3.2746527978219 | | 1986 | 3.4253449096514 | | 1985 | 3.5264232543043 | | 1984 | 3.5704896324805 | | 1983 | 3.5320695369152 | | 1982 | 4.8789374758536 | | 1981 | 4.9520582474037 | | 1980 | 3.4751314315337 | | 1979 | 3.3100670646278 | | 1978 | 3.1529675666814 | | 1977 | 3.0138305826964 | | 1976 | 2.9510776530391 | | 1975 | 2.9698081604234 | | 1974 | 2.9062901545333 | | 1973 | 2.8493482325502 | | 1972 | 2.8220728998034 | | 1971 | 2.8551095670976 | | 1970 | 2.8740480163545 | | 1969 | 2.8189587692502 | | 1968 | 2.7995791538436 | | 1967 | 2.8513940443225 | | 1966 | 2.923061961481 | | 1965 | 2.9556502818226 | | 1964 | 2.9214673836209 | | 1963 | 2.8522862698942 | | 1962 | 2.7875611075174 | | 1961 | 2.7430020509535 |
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