| Year | Value | | 2014 | -28.319820891588 | | 2013 | -22.823751532008 | | 2012 | -21.171500670037 | | 2011 | -21.291263762655 | | 2010 | -20.64790147557 | | 2009 | -27.925455212873 | | 2008 | -45.455088475787 | | 2007 | -45.839245795869 | | 2006 | -52.60845889302 | | 2005 | -49.793090778524 | | 2004 | -54.725274004462 | | 2003 | -60.630525041512 | | 2002 | -68.934270306266 | | 2001 | -67.52976318677 | | 2000 | -76.628654041154 | | 1999 | -81.659198042655 | | 1998 | -87.402441274894 | | 1997 | -86.933331459853 | | 1996 | -81.720002030212 | | 1995 | -77.643732202041 | | 1994 | -92.722336754605 | | 1993 | -98.665737626689 | | 1992 | -113.17562630105 | | 1991 | -113.30340262771 | | 1990 | -120.35425680356 | | 1989 | -134.93151476834 | | 1988 | -152.80634156806 | | 1987 | -172.96483007456 | | 1986 | -174.63762669692 | | 1985 | -180.04564218733 | | 1984 | -188.83145972632 | | 1983 | -125.48323257842 | | 1982 | -125.39581616311 | | 1981 | -110.25597526218 | | 1980 | -83.484440544041 | | 1979 | -42.467114916743 | | 1978 | 0.68113629803083 | | 1977 | 12.89930977915 | | 1976 | 10.471191101924 | | 1975 | 11.390823420199 | | 1974 | 9.4720730380714 | | 1973 | 9.3725505655608 | | 1972 | 9.2191296059077 | | 1971 | 9.007062594961 |
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