| Year | Value | | 2010 | 0.00014496885585747 | | 2009 | 0.00090646862485472 | | 2008 | 0.00080465462724532 | | 2007 | 0.0036699474543464 | | 2006 | 0.0040433337556371 | | 2005 | 0.017725792005957 | | 2004 | 0.74333988124428 | | 2003 | 3.3557415442969 | | 2002 | 3.5509195009424 | | 2001 | 3.7937115300754 | | 2000 | 4.6191826322945 | | 1999 | 5.5604580888581 | | 1998 | 6.0684554498182 | | 1997 | 8.7213231755781 | | 1996 | 15.238093487559 | | 1995 | 18.44699182783 | | 1994 | 13.707987977047 | | 1993 | 13.895512681552 | | 1992 | 13.604887983707 | | 1991 | 9.4635322483424 | | 1990 | 8.5775085938779 | | 1989 | 9.4365109996141 | | 1988 | 7.2081016679905 | | 1987 | 7.9212454212454 | | 1986 | 8.4365325077399 | | 1985 | 8.574091332712 | | 1984 | 7.768641905302 | | 1983 | 8.3503649635036 | | 1982 | 7.8666666666667 | | 1981 | 8.1875437368789 |
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