| Year | Value | | 2021 | 5.8596986020635 | | 2020 | -6.5221866657783 | | 2019 | 0.36443833720084 | | 2018 | 3.0150740298072 | | 2017 | 4.7320768049957 | | 2016 | 0.85312271040776 | | 2015 | 3.2834512356489 | | 2014 | 1.290643207258 | | 2013 | 0.27643391915895 | | 2012 | -2.125193688028 | | 2011 | 1.6158583600351 | | 2010 | 3.9745101836531 | | 2009 | -3.3699113000744 | | 2008 | -2.9389949020192 | | 2007 | 3.110596970681 | | 2006 | 4.8503048745514 | | 2005 | 2.2302477363926 | | 2004 | 1.4466218371978 | | 2003 | 1.5518141133797 | | 2002 | 0.21042710677011 | | 2001 | 0.022975752944859 | | 2000 | 3.7257013452961 | | 1999 | 5.9988537782362 | | 1998 | 4.0504365143142 | | 1997 | 5.1041062734388 | | 1996 | 4.1509949799002 | | 1995 | 4.4640410365235 | | 1994 | 4.2878722765778 | | 1993 | 1.7658670032243 | | 1992 | 0.62342014596335 | | 1991 | 3.1577352376034 | | 1990 | 2.152028440643 | | 1989 | 4.3407266052534 | | 1988 | 2.4353902840513 | | 1987 | 1.3861309974279 | | 1986 | 2.8296390278963 | | 1985 | 0.0029460850933702 | | 1984 | 4.0319485579565 | | 1983 | 1.8094170872769 | | 1982 | 0.49060236808214 | | 1981 | 0.30712081522211 | | 1980 | 0.95093635758614 | | 1979 | 0.81073768507431 | | 1978 | 2.0331331427204 | | 1977 | 1.878268650495 | | 1976 | 5.6758039840332 | | 1975 | -1.5147790080368 | | 1974 | 0.95863467840873 | | 1973 | 6.7304033557232 | | 1972 | 3.5968958288167 | | 1971 | 3.0143976886894 |
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