| Year | Value | | 2021 | 3.9920105995033 | | 2020 | 1.7887456939642 | | 2019 | 5.3681828310158 | | 2018 | 5.9223890781152 | | 2017 | 7.2583919000067 | | 2016 | 10.319276732185 | | 2015 | 13.312472437328 | | 2014 | 11.888753998136 | | 2013 | 15.24484072125 | | 2012 | -4.122541682403 | | 2011 | 2.8669967465306 | | 2010 | 3.6137348296904 | | 2009 | 1.9757759307205 | | 2008 | 2.5532396842821 | | 2007 | 3.5648058655053 | | 2006 | 9.758599887492 | | 2005 | 10.293580858524 | | 2004 | 7.158673153257 | | 2003 | 4.8934163299313 | | 2002 | 11.726065520228 | | 2001 | 6.332657270505 | | 2000 | 5.3714473879912 | | 1999 | 7.1964643942283 | | 1998 | 18.055341695528 | | 1997 | 12.720211646458 | | 1996 | 7.8566665298421 | | 1995 | 10.307379572856 | | 1994 | 4.6543937909289 | | 1993 | -3.3121381225074 | | 1992 | -4.6436253178429 | | 1991 | 6.4647645795814 |
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