| Year | Value | | 2020 | 0.8770574492427 | | 2019 | 0.87430655659086 | | 2018 | 0.8863072726298 | | 2017 | 0.89465981525855 | | 2016 | 0.90637961916164 | | 2015 | 0.91433693097196 | | 2014 | 0.94147934646676 | | 2013 | 0.9602576052142 | | 2012 | 0.97960481219017 | | 2011 | 0.98928388578353 | | 2010 | 1.0179232377406 | | 2009 | 1.0194708953543 | | 2008 | 1.0387522364549 | | 2007 | 1.0505811502845 | | 2006 | 1.058483096039 | | 2005 | 1.1031052231995 | | 2004 | 1.0749503978712 | | 2003 | 1.1145323994189 | | 2002 | 1.1264704218221 | | 2001 | 1.1336777750784 | | 2000 | 1.1787552829795 | | 1999 | 1.2497758141671 | | 1998 | 1.2814859499291 | | 1997 | 1.2943013351035 | | 1996 | 1.3249162019143 | | 1995 | 1.3577763345546 | | 1994 | 1.3537407589315 | | 1993 | 1.3709799819259 | | 1992 | 1.4238091633445 | | 1991 | 1.5346548241114 |
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