| Year | Value | | 2021 | 4.61118287645 | | 2020 | -7.5213492109631 | | 2019 | 2.6252850493096 | | 2018 | 2.1581759111003 | | 2017 | 0.52954349558745 | | 2016 | 2.853834892132 | | 2015 | 5.5245071884148 | | 2014 | 7.2806278714265 | | 2013 | 1.6107647079013 | | 2012 | 2.1313867056535 | | 2011 | -4.7815634545369 | | 2010 | 44.289447426086 | | 2009 | 7.8793480117302 | | 2008 | 0.35229591659275 | | 2007 | 2.8940659271071 | | 2006 | 4.4140917766262 | | 2005 | 3.2932080988104 | | 2004 | 4.6580722525717 | | 2003 | 5.1864094289105 | | 2002 | 1.8443113587938 | | 2001 | 11.964529992927 | | 2000 | 2.2445918752096 | | 1999 | 5.9558021083682 | | 1998 | 5.666438608736 | | 1997 | 7.4413337593377 | | 1996 | 7.6196828019761 | | 1995 | 4.2423579703684 | | 1994 | 4.7389680824258 | | 1993 | 0.61308500251035 | | 1992 | -1.4754457447725 | | 1991 | 1.434407317932 | | 1990 | 9.6666924147671 | | 1989 | 2.483974984895 | | 1988 | 1.3572081963849 | | 1987 | 6.3199529673611 | | 1986 | -3.3475365176386 | | 1985 | 0.95800970516046 | | 1984 | 2.0265213238404 | | 1983 | 4.0480768157327 | | 1982 | 0.84985425468163 | | 1981 | 8.2850679196395 | | 1980 | 6.0197876251948 | | 1979 | 4.6589139559155 | | 1978 | 8.3393230029074 | | 1977 | 1.3414014056239 | | 1976 | 2.2900473310152 | | 1975 | 4.5036807597941 | | 1974 | 12.387904530027 | | 1973 | -1.6388715485713 | | 1972 | 19.782832382761 | | 1971 | 9.0443018689668 |
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