| Year | Value | | 2022 | 1.478808650003 | | 2021 | 1.5607751592689 | | 2020 | 1.676415479414 | | 2019 | 1.4535077317825 | | 2018 | 1.5372588618059 | | 2017 | 1.5760110887505 | | 2016 | 1.6973895707374 | | 2015 | 1.752024086722 | | 2014 | 1.7135690234793 | | 2013 | 1.6223608216927 | | 2012 | 1.6279722149908 | | 2011 | 1.3944280044239 | | 2010 | 1.6110185266278 | | 2009 | 1.4331099181554 | | 2008 | 1.1891989096339 | | 2007 | 1.3388218589871 | | 2006 | 1.6656395073466 | | 2005 | 1.6144018114118 | | 2004 | 1.6833067779835 | | 2003 | 1.6967287975472 | | 2002 | 1.6150870787947 | | 2001 | 1.4544225657219 | | 2000 | 1.8826786815366 | | 1999 | 1.8512475894469 | | 1998 | 1.5906340875447 | | 1997 | 1.7630186862284 | | 1996 | 1.5479800677798 | | 1995 | 1.7905169370273 | | 1994 | 1.0902815911209 | | 1993 | 0.82505555866809 | | 1992 | 0.85295567864794 |
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