| Year | Value | | 2021 | -5.4612479467925 | | 2020 | 0.67806396779379 | | 2019 | 6.5051159101353 | | 2018 | 7.8537030060398 | | 2017 | 6.5038453574947 | | 2016 | 8.4574218057961 | | 2015 | 5.5647649146916 | | 2014 | 3.2216932665231 | | 2013 | 3.3414296894724 | | 2012 | 12.380515078473 | | 2011 | 6.0728190574994 | | 2010 | 8.1693718771229 | | 2009 | 2.2861895437 | | 2008 | 4.9456614734169 | | 2007 | 3.8296832935506 | | 2006 | 5.6538956399723 | | 2005 | 7.2599950800755 | | 2004 | 4.6746116006676 | | 2003 | 7.5367400108234 | | 2002 | 4.1683448736987 | | 2001 | 6.5349756907003 | | 2000 | 3.805636045835 | | 1999 | 3.226486945417 | | 1998 | 8.8869849304161 | | 1997 | 4.9180602847726 | | 1996 | 10.729319875099 | | 1995 | 8.1310042247741 | | 1994 | -7.2065047369187 | | 1993 | 2.8635412113948 | | 1992 | 0.38015142661052 | | 1991 | 7.2910292709557 | | 1990 | 0.2532088225212 | | 1989 | 0.29859062419679 | | 1988 | 5.9445907491148 | | 1987 | 0.67736503498622 | | 1986 | 9.7738701110187 | | 1985 | 1.1854391188705 | | 1984 | -1.2414141284234 | | 1983 | 0.22342819190369 | | 1982 | 8.1561590032027 | | 1981 | 3.933077089581 |
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