| Year | Value | | 2020 | 0.84970109403736 | | 2019 | 0.84616606855261 | | 2018 | 0.87261303974752 | | 2017 | 0.90086573196842 | | 2016 | 0.93057785783045 | | 2015 | 0.96052457448761 | | 2014 | 1.1552909022492 | | 2013 | 1.1900255458817 | | 2012 | 1.2252399428221 | | 2011 | 1.2622043136133 | | 2010 | 1.3029720171248 | | 2009 | 1.2695787175078 | | 2008 | 1.3886504337639 | | 2007 | 1.4507203485949 | | 2006 | 1.5155773798698 | | 2005 | 1.5592817664678 | | 2004 | 1.458776436676 | | 2003 | 1.5773344549934 | | 2002 | 1.626071658655 | | 2001 | 1.5991454166893 | | 2000 | 1.6543117153393 | | 1999 | 1.7007901871209 | | 1998 | 1.6636487494615 | | 1997 | 1.5338419673598 | | 1996 | 1.583696496677 | | 1995 | 1.6380521440175 | | 1994 | 1.3956288903155 | | 1993 | 1.4460509381772 | | 1992 | 1.4999828573388 | | 1991 | 1.5542637896504 |
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