| Year | Value | | 2014 | -48.803135597339 | | 2013 | -48.127370295377 | | 2012 | -51.570981045587 | | 2011 | -54.577362141039 | | 2010 | -58.184646977025 | | 2009 | -55.215997987341 | | 2008 | -57.501145133187 | | 2007 | -61.368350788369 | | 2006 | -62.200928978355 | | 2005 | -60.945792249293 | | 2004 | -58.446942954958 | | 2003 | -58.419381363575 | | 2002 | -55.417231846751 | | 2001 | -59.05236006322 | | 2000 | -61.156440239032 | | 1999 | -57.085784663467 | | 1998 | -60.708710198746 | | 1997 | -61.604788392262 | | 1996 | -57.661439530739 | | 1995 | -55.667607952673 | | 1994 | -56.053775182838 | | 1993 | -54.220408231604 | | 1992 | -55.300826062492 | | 1991 | -51.913164694274 | | 1990 | -52.636811468232 | | 1989 | -50.881590373532 | | 1988 | -44.655690381893 | | 1987 | -41.70996309132 | | 1986 | -45.998026526532 | | 1985 | -47.533956591945 | | 1984 | -42.701974940359 | | 1983 | -36.131913155167 | | 1982 | -35.270139625277 | | 1981 | -39.922765928253 | | 1980 | -57.154007103101 | | 1979 | -64.256307307553 | | 1978 | -50.949382846651 | | 1977 | -58.807740948531 | | 1976 | -58.9288655699 | | 1975 | -51.123041831316 | | 1974 | -67.31916369935 | | 1973 | -60.847683199386 | | 1972 | -54.48266794988 | | 1971 | -45.644267015503 |
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