| Year | Value | | 2021 | 13.017994517714 | | 2020 | -11.163826921419 | | 2019 | 4.7751403010094 | | 2018 | -1.480644057107 | | 2017 | -1.1585685506335 | | 2016 | 0.76465188493569 | | 2015 | 10.411355617058 | | 2014 | 5.130165269566 | | 2013 | 5.9699113105134 | | 2012 | 5.5737394511431 | | 2011 | 3.9652335254186 | | 2010 | -3.6307422724096 | | 2009 | 5.2110558649852 | | 2008 | -5.0178924806355 | | 2007 | 0.64409909005919 | | 2006 | 1.6773488820365 | | 2005 | 2.129825837727 | | 2004 | 0.91092802678934 | | 2003 | 1.2115170320787 | | 2002 | 4.2860689702692 | | 2001 | 3.6623602787727 | | 2000 | 0.76692335188986 | | 1999 | 6.2279733693505 | | 1998 | 3.8713790540834 | | 1997 | -4.9195167518398 | | 1996 | 0.085665159256095 | | 1995 | 2.439407237548 | | 1994 | 1.9607475644709 | | 1993 | 5.4122833652208 | | 1992 | 5.7198214557285 | | 1991 | 7.4073470730014 | | 1990 | 43.358444487532 | | 1989 | 9.6430654832838 | | 1988 | 13.454976635506 | | 1987 | 19.817376539351 | | 1986 | 9.6877003217907 | | 1985 | -9.8543135063443 | | 1984 | 0.86043403220042 | | 1983 | 0.56659513425376 | | 1982 | -2.5569267662317 | | 1981 | -20.041680599958 |
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