| Year | Value | | 2020 | 1.0513557232051 | | 2019 | 1.0119599206045 | | 2018 | 0.99271318886146 | | 2017 | 1.0639914880681 | | 2016 | 1.0466346011151 | | 2015 | 1.0790353102226 | | 2014 | 1.1132138483803 | | 2013 | 1.1519489428719 | | 2012 | 1.1941703100743 | | 2011 | 1.2381703907259 | | 2010 | 1.2835273630792 | | 2009 | 1.3307882835016 | | 2008 | 1.4404240608435 | | 2007 | 1.4911701425133 | | 2005 | 1.5930017158904 | | 2004 | 1.4106262475226 | | 2003 | 1.6256256839153 | | 2002 | 1.6762446116241 | | 2001 | 1.7273338987989 | | 2000 | 1.7789814667304 | | 1999 | 2.5968274968496 | | 1998 | 2.672435376293 | | 1997 | 2.7496063721404 | | 1996 | 2.8286774295362 | | 1995 | 2.9095764881718 | | 1994 | 1.8889605994302 | | 1993 | 2.2649397040694 | | 1992 | 2.3274062055299 | | 1991 | 3.4156038446037 |
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