| Year | Value | | 2021 | 5.2265836223092 | | 2020 | -3.4310901335395 | | 2019 | 2.2625721141811 | | 2018 | 2.9093593134841 | | 2017 | 2.70757763143 | | 2016 | 1.0584842664596 | | 2015 | 3.5424162077108 | | 2014 | 3.3495061803628 | | 2013 | 1.4109982732616 | | 2012 | 3.8505580308473 | | 2011 | 2.0490275741386 | | 2010 | 4.3133761107795 | | 2009 | -1.0745452665822 | | 2008 | -2.683324477306 | | 2007 | 0.32034418660164 | | 2006 | 3.7610552560744 | | 2005 | 2.7528077144267 | | 2004 | 3.8447431864914 | | 2003 | 1.922753915665 | | 2002 | 1.4726831394584 | | 2001 | 1.5221721233393 | | 2000 | 3.8205447073679 | | 1999 | 4.1665793735241 | | 1998 | 5.9127755776203 | | 1997 | 5.4183172184823 | | 1996 | 4.3407602411957 | | 1995 | 3.3513144434315 | | 1994 | 4.4667739450144 | | 1993 | 2.2787467049467 | | 1992 | 3.4674210805846 | | 1991 | 0.32685699282003 | | 1990 | 1.3265012059977 | | 1989 | 2.317167658288 | | 1988 | 5.7841678063713 | | 1987 | 3.6214556745539 | | 1986 | 3.5041822481838 | | 1985 | 4.1689011843169 | | 1984 | 8.0973857200099 | | 1983 | 3.2015782995547 | | 1982 | 1.1748705547807 | | 1981 | 4.2911249344252 | | 1980 | -2.2565871600196 | | 1979 | 0.64055215727736 | | 1978 | 5.1365206588284 | | 1977 | 4.0336303067931 | | 1976 | 5.0297582350246 | | 1975 | 0.35318296553818 | | 1974 | -4.35892150478 | | 1973 | 5.464157086095 | | 1972 | 5.4374731011387 | | 1971 | 2.6652730601457 |
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