| Year | Value | | 2021 | 6.4980487683657 | | 2020 | -2.5045656274326 | | 2019 | 3.2293558023373 | | 2018 | 3.4522753242599 | | 2017 | 5.5836549233245 | | 2016 | 4.7480700718037 | | 2015 | 4.1357210881261 | | 2014 | 4.8900876437579 | | 2013 | 4.402331994619 | | 2012 | 5.8676877349258 | | 2011 | 4.91190870997 | | 2010 | 8.0043630095417 | | 2009 | 4.4586316827182 | | 2008 | 4.3092415980154 | | 2007 | 15.474359685268 | | 2006 | 11.35302687277 | | 2005 | 6.8746576456569 | | 2004 | 12.655992972293 | | 2003 | 0.17553461336604 | | 2002 | 12.94991188636 | | 2001 | 3.5364314400389 | | 2000 | 3.5350869982943 | | 1999 | 1.8858453931737 | | 1998 | -4.2202753786448 | | 1997 | 4.2940766626736 | | 1996 | 0.18503197602131 |
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