| Year | Value | | 2021 | 3.2439863425985 | | 2020 | 0.1571079379035 | | 2019 | 8.3513857476585 | | 2018 | -2.2618810708547 | | 2017 | -1.3021057874975 | | 2016 | 5.6046966249744 | | 2015 | -5.8410705456953 | | 2014 | 9.2084626770491 | | 2013 | 6.3131096436299 | | 2012 | 0.99009233628753 | | 2011 | 19.788430952676 | | 2010 | 11.19814014964 | | 2009 | -6.3602697531466 | | 2008 | 11.70647716273 | | 2007 | 10.719453794669 | | 2006 | 10.331046522718 | | 2005 | 20.789435019358 | | 2004 | 2.7107577277862 | | 2003 | -6.4516037679122 | | 2002 | -11.213642029369 | | 2001 | 2.7489350464687 | | 2000 | -1.886582157905 | | 1999 | 10.911531648103 | | 1998 | -2.6062116154044 | | 1997 | 12.490367180572 | | 1996 | 12.867847863571 | | 1995 | 11.917784699164 | | 1994 | -11.706523895525 | | 1993 | 9.3701457515324 | | 1992 | 3.5344850315234 | | 1991 | 9.7155343005382 | | 1990 | 14.983475127178 | | 1989 | 4.8554992392156 | | 1988 | 18.763498979747 | | 1987 | 13.525507920906 | | 1986 | 15.171034096802 | | 1985 | 30.609504811912 | | 1984 | 8.3433696801635 | | 1983 | 5.2886198171549 | | 1982 | 3.4726910173936 | | 1981 | 6.6373552200048 | | 1980 | 0.44853412048164 | | 1979 | 17.917862811843 | | 1978 | 18.114807221249 | | 1977 | 8.962402583335 | | 1976 | 11.553035097942 |
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