| Year | Value | | 2020 | 0.84980893462453 | | 2019 | 0.86255229223272 | | 2018 | 0.88376712147171 | | 2017 | 0.90639450660948 | | 2016 | 0.92703182839692 | | 2015 | 0.95294603830505 | | 2014 | 0.97929560886162 | | 2013 | 1.0055164851261 | | 2012 | 1.0302439467591 | | 2011 | 1.0490706947677 | | 2010 | 1.0612038898554 | | 2009 | 1.0708746136525 | | 2008 | 1.0825559272803 | | 2007 | 1.0877354627355 | | 2006 | 1.095524353399 | | 2005 | 1.1010120243466 | | 2004 | 1.0803490132308 | | 2003 | 1.1013564462089 | | 2002 | 1.2608555188279 | | 2001 | 1.3349428763013 | | 2000 | 1.3692596337829 | | 1999 | 1.3682762891897 | | 1998 | 1.4019666733153 | | 1997 | 1.4436301599984 | | 1996 | 1.5866983745157 | | 1995 | 1.7117438504087 | | 1994 | 1.1098449701439 | | 1993 | 1.2537724183651 | | 1992 | 1.2745104286816 | | 1991 | 1.2316976570921 |
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