| Year | Value | | 2022 | 7.9309292543009 | | 2021 | 1.8621529749465 | | 2020 | 0.60579580839539 | | 2019 | 1.1066667429606 | | 2018 | 1.2569956669051 | | 2017 | 0.78441525110133 | | 2016 | -1.4078163709171 | | 2015 | 0.13118799902455 | | 2014 | 0.23877814499062 | | 2013 | 1.5065428570141 | | 2012 | 2.5403964416711 | | 2011 | 4.4738834216502 | | 2010 | 2.0786647090642 | | 2009 | 0.99110348056808 | | 2008 | 6.7744354637114 | | 2007 | 4.4109970419349 | | 2006 | 5.3690768706555 | | 2005 | 0.41889161285517 | | 2004 | -1.8908217230618 | | 2003 | 1.1881703862053 | | 2002 | 1.8845341007676 | | 2001 | 3.3499647231789 | | 2000 | -2.4774566851984 | | 1999 | 4.3564337451045 | | 1998 | 4.3942350998348 | | 1997 | 8.5560625814863 | | 1996 | 5.9636196177758 | | 1995 | 8.3515249797293 | | 1994 | 3.4520583301071 | | 1993 | 5.788395904437 | | 1992 | 3.1166643268286 | | 1991 | 9.5509074131036 | | 1990 | 10.653505786249 | | 1989 | 4.5551601423488 | | 1988 | 4.0740740740738 | | 1987 | 3.8461538461541 | | 1986 | 10.874200426439 | | 1985 | 5.3932584269664 | | 1984 | 11.25 |
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