| Year | Value | | 2021 | 7.4721784460922 | | 2020 | 5.7222689795953 | | 2019 | -6.695735099356 | | 2018 | -11.434704865111 | | 2017 | 0.50436742695702 | | 2016 | 19.995315059171 | | 2015 | -16.578495069193 | | 2014 | -1.5432076481525 | | 2013 | -2.8335521082678 | | 2012 | -11.137557526485 | | 2011 | 2.5429739632391 | | 2010 | 9.9656364376019 | | 2009 | 3.096073558354 | | 2008 | -3.5270671045573 | | 2007 | 14.98074824823 | | 2006 | 5.2662659308015 | | 2005 | 10.270746407838 | | 2004 | 3.6859612020137 | | 2003 | 6.0675846874868 | | 2002 | 18.392296535596 | | 2001 | 13.169498288816 | | 2000 | 1.7631972337054 | | 1999 | 8.4784287339064 | | 1998 | 0.78213700035721 | | 1997 | 3.1890638376423 | | 1996 | 8.6997530939258 | | 1995 | -1.4889086355582 | | 1994 | -1.0455213085285 | | 1990 | 9.9769457562713 | | 1989 | 3.7605602803123 | | 1988 | -17.498342979601 | | 1987 | -1.7095621740614 | | 1986 | -9.5762573245286 | | 1985 | 4.1731534384022 | | 1984 | -9.0009284744796 | | 1983 | 13.633345125684 | | 1982 | 20.350893753947 | | 1981 | 0.79740788395651 | | 1980 | -19.951013222856 | | 1979 | 2.9583647749234 | | 1978 | -17.455872821557 | | 1977 | 0.02202616493075 | | 1976 | 23.854262084131 | | 1975 | 19.288746811885 | | 1974 | 24.232372968914 | | 1973 | 23.457680245492 | | 1972 | 22.869413182659 | | 1971 | 14.815774833549 |
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