| Year | Value | | 2021 | 4.860841970138 | | 2020 | -6.8074440124406 | | 2019 | 1.2513165981915 | | 2018 | 0.40926695345595 | | 2017 | 3.2296955905475 | | 2016 | 0.44879757239281 | | 2015 | 0.91434858645387 | | 2014 | 1.2425376083198 | | 2013 | 3.5228453414945 | | 2012 | 1.3378495780939 | | 2011 | 4.2562343176764 | | 2010 | 6.6584787378799 | | 2009 | -2.0479784361673 | | 2008 | 2.9140400612525 | | 2007 | 6.6391427677404 | | 2006 | 7.700047174103 | | 2005 | 2.7576109551217 | | 2004 | 4.339393501022 | | 2003 | 1.3427291089948 | | 2002 | 0.44604193244983 | | 2001 | 0.4372113931317 | | 2000 | 2.5867388513577 | | 1999 | 0.89685483958 | | 1998 | 2.1082743075564 | | 1997 | 5.6831575847838 | | 1996 | 3.1529603119389 | | 1995 | 2.3984383730728 | | 1994 | 12.07842477113 | | 1993 | 3.0067639882044 | | 1992 | 4.6288984210544 | | 1991 | 6.6736742866269 | | 1990 | -2.2427135923774 |
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