| Year | Value | | 2020 | 1.1316463893044 | | 2019 | 1.1388553517541 | | 2018 | 1.1306394261239 | | 2017 | 1.1432469595598 | | 2016 | 1.138009694025 | | 2015 | 1.130672397231 | | 2014 | 1.127974957787 | | 2013 | 1.1314697216657 | | 2012 | 1.1008910651846 | | 2011 | 1.1610661667766 | | 2010 | 1.0635965646105 | | 2009 | 1.0591270098416 | | 2008 | 1.0658191151544 | | 2007 | 1.0738177062517 | | 2006 | 1.0972837394176 | | 2005 | 1.1037193954145 | | 2004 | 1.1180895196373 | | 2003 | 1.1630729880301 | | 2002 | 1.1569826984697 | | 2001 | 1.1495086887717 | | 2000 | 1.1971012907746 | | 1999 | 1.1044527874411 | | 1998 | 1.1097016297838 | | 1997 | 0.9954249442503 | | 1996 | 1.1870715211044 | | 1995 | 1.2961626157912 | | 1994 | 0.91437525279323 | | 1993 | 0.94885235503546 | | 1992 | 0.92996633817605 | | 1991 | 0.9511318216611 |
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