| Year | Value | | 2021 | -2.8688836899579 | | 2020 | 6.5670178515066 | | 2019 | 10.509574944246 | | 2018 | 17.672913593715 | | 2017 | 5.0643357342147 | | 2016 | 12.048975149341 | | 2015 | 4.2675900331711 | | 2014 | -10.009666492937 | | 2013 | 5.7689677292346 | | 2012 | 0.44169084160231 | | 2011 | 14.653850380278 | | 2010 | 7.3189041966306 | | 2009 | 10.545274043453 | | 2008 | 1.2522729576983 | | 2007 | -1.7232452672618 | | 2006 | 6.3450248146318 | | 2005 | 8.0740558207597 | | 2004 | 1.362908360402 | | 2003 | 12.906152239288 | | 2002 | 9.4916977601973 | | 2001 | -5.5594862145906 | | 2000 | -4.5366022664011 | | 1999 | 4.4806149352967 | | 1998 | 10.045066699808 | | 1997 | -3.9268062092673 | | 1996 | 4.2603779072346 | | 1995 | 17.436739128199 | | 1994 | 0.14651837162106 | | 1993 | 6.7006825333945 | | 1992 | -12.826953520767 | | 1991 | 3.2769993071162 | | 1990 | -2.6527043899533 | | 1989 | 7.9198181596422 | | 1988 | 0.94194055061152 | | 1987 | 3.7323967653063 | | 1986 | 9.9858069066336 | | 1985 | 1.4237715744707 | | 1984 | 0.47192189202062 | | 1983 | 0.47817686804439 | | 1982 | -1.1691456243093 | | 1981 | 4.2305703693554 |
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