| Year | Value | | 2021 | 9.0865116593666 | | 2020 | -4.5374127075444 | | 2019 | 2.2965029673208 | | 2018 | 0.73155091180507 | | 2017 | 6.6358035731713 | | 2016 | 3.5201876038667 | | 2015 | 9.885470143967 | | 2014 | 4.0835820932865 | | 2013 | 0.31384106300877 | | 2012 | 1.0890373878477 | | 2011 | 7.1360450023487 | | 2010 | 0.0027712098795973 | | 2009 | 1.1895128781262 | | 2008 | 1.3689811640904 | | 2007 | 7.2878048796854 | | 2006 | 4.7009266931836 | | 2005 | 5.0896120108867 | | 2004 | 3.5691262983391 | | 2003 | 2.610252841464 | | 2002 | 2.1417431383881 | | 2001 | 1.6724944716107 | | 2000 | 6.4802448855677 | | 1999 | 1.6241161084694 | | 1998 | 6.063659512869 | | 1997 | 5.0406765367136 | | 1996 | 0.16973408068729 | | 1995 | 5.4236640335457 | | 1994 | 3.4342512134157 | | 1993 | 13.042653418378 | | 1992 | 4.0522629359475 | | 1991 | 0.052420687654717 | | 1990 | -1.6843078285486 | | 1989 | 0.59290829890134 | | 1988 | 4.0654242415911 | | 1987 | 6.294293031988 | | 1986 | 7.3516337955367 | | 1985 | 6.9424579965985 | | 1984 | 13.01551606482 | | 1983 | 5.3981610696683 | | 1982 | -10.079403663908 | | 1981 | -8.2989877924797 | | 1980 | 0.1703928214486 | | 1979 | 0.5435512961278 | | 1978 | 3.0930264063225 | | 1977 | 14.994477924698 | | 1976 | 19.398995646081 | | 1975 | 1.4354663465344 | | 1974 | -3.8055327675114 | | 1973 | 6.1775110156925 | | 1972 | 5.8653027660636 |
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