| Year | Value | | 2020 | 1.174178637581 | | 2019 | 1.1318936746244 | | 2018 | 1.1367617083483 | | 2017 | 1.1487331866146 | | 2016 | 1.1483284853691 | | 2015 | 1.1598307423572 | | 2014 | 1.1647477163757 | | 2013 | 1.1703139820203 | | 2012 | 1.1723260420213 | | 2011 | 1.2025166308302 | | 2010 | 1.227930013127 | | 2009 | 1.2543745656925 | | 2008 | 1.287077898781 | | 2007 | 1.3156343961649 | | 2006 | 1.3434104040419 | | 2005 | 1.3419806377892 | | 2004 | 1.3550057371519 | | 2003 | 1.3708183114493 | | 2002 | 1.3893992385501 | | 2001 | 1.4103492024625 | | 2000 | 1.4331107742793 | | 1999 | 1.4572351103127 | | 1998 | 1.482462313127 | | 1997 | 1.5087851422544 | | 1996 | 1.9140492867691 | | 1995 | 1.9851955315794 | | 1994 | 1.2228877060653 | | 1993 | 1.261359442753 | | 1992 | 1.3040155855943 | | 1991 | 1.3412294705669 |
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