| Year | Value | | 2021 | 6.387623001203 | | 2020 | -9.3381711555582 | | 2019 | 2.9029854608884 | | 2018 | 0.96449184484071 | | 2017 | 1.0238772191742 | | 2016 | 0.27958817924957 | | 2015 | 5.7502451084202 | | 2014 | 1.5896871802051 | | 2013 | 4.7330660393133 | | 2012 | 10.83224588051 | | 2011 | 2.9777195781372 | | 2010 | 11.234036578464 | | 2009 | 4.2313342745845 | | 2008 | 1.7070008739235 | | 2007 | 8.2791472246473 | | 2006 | 4.22117531094 | | 2005 | 8.8657998124908 | | 2004 | 6.0612675055561 | | 2003 | 4.3743243652861 | | 2002 | 3.2318178045162 | | 2001 | 3.9415635293328 | | 2000 | 3.7219952799588 | | 1999 | -1.0732851431391 | | 1998 | 5.9552725420469 | | 1997 | 7.9803678489412 | | 1996 | 6.9441076302183 | | 1995 | 14.244130244765 | | 1994 | 7.9208693933949 | | 1993 | 7.2712455565184 | | 1992 | 13.450483624334 | | 1991 | 13.093783511711 | | 1990 | 4.8658229089201 | | 1989 | 8.5342289713944 | | 1988 | 10.278681244802 | | 1987 | 11.602763978477 | | 1986 | 9.295043657589 | | 1985 | -1.8311512590793 | | 1984 | -4.2135451605625 | | 1983 | -27.823570163511 | | 1982 | 9.5939192046102 | | 1981 | 6.2273840638598 | | 1980 | 5.981192919933 | | 1979 | 9.087571986357 | | 1978 | 7.3119951390839 | | 1977 | 12.995243694258 | | 1976 | 7.5844255655948 | | 1975 | -21.763303903997 | | 1974 | -12.585973799681 | | 1973 | -7.610155886785 | | 1972 | 2.8972064779396 | | 1971 | 12.570645538811 |
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