| Year | Value | | 2014 | 47.833735002663 | | 2013 | 37.728596410072 | | 2012 | 5.4555993515808 | | 2011 | -26.152090204209 | | 2010 | -27.74548348214 | | 2009 | -12.474388119465 | | 2008 | -4.2729469920708 | | 2007 | -6.238144460261 | | 2006 | -16.318604154854 | | 2005 | -27.008382866046 | | 2004 | -62.233887459414 | | 2003 | -119.44362701953 | | 2002 | -125.16888439578 | | 2001 | -116.91864926704 | | 2000 | -111.72747929422 | | 1999 | -121.35141094979 | | 1998 | -120.03665668182 | | 1997 | -138.02585321657 | | 1996 | -152.32878584815 | | 1995 | -173.41418783293 | | 1994 | -171.98067083848 | | 1993 | -162.11566288006 | | 1992 | -154.27543249347 | | 1991 | -133.13093012744 | | 1990 | -113.26237252285 | | 1989 | -104.89096277426 | | 1988 | -64.327895265477 | | 1987 | -45.14261025193 | | 1986 | -23.278464961898 | | 1985 | -23.87527140102 | | 1984 | -16.72503976807 | | 1983 | -32.366049938785 | | 1982 | -46.142043961051 | | 1981 | -83.898908137968 | | 1980 | -112.7893831122 | | 1979 | -64.665368907855 | | 1978 | -142.16038804634 | | 1977 | -143.01589663958 | | 1976 | -195.454900425 | | 1975 | -216.96914786743 | | 1974 | -144.86039887547 | | 1973 | -170.58910116213 | | 1972 | -197.64825757472 | | 1971 | -123.50250490089 |
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