| Year | Value | | 2022 | 4.0563163324672 | | 2021 | 3.7204513646667 | | 2020 | 4.1714789011807 | | 2019 | 3.8603375043707 | | 2018 | 3.7198224395643 | | 2017 | 4.2489960517395 | | 2016 | 5.425147705045 | | 2015 | 4.871514746802 | | 2014 | 4.1129929782232 | | 2013 | 3.8540425831437 | | 2012 | 3.6892404345991 | | 2011 | 3.4330438376013 | | 2010 | 3.5850857201211 | | 2009 | 3.9240634030283 | | 2008 | 3.1494860200222 | | 2007 | 3.1185420747754 | | 2006 | 3.2463572340584 | | 2005 | 3.3312372344166 | | 2004 | 3.3003536466048 | | 2003 | 3.670838089601 | | 2002 | 3.7562773910802 | | 2001 | 3.5463192290882 | | 2000 | 3.3070298366754 | | 1999 | 3.0732879223511 | | 1998 | 2.7326490886569 | | 1997 | 4.0398092967819 | | 1996 | 3.7565588208028 | | 1995 | 3.7844299674267 | | 1994 | 4.5237006553879 | | 1993 | 4.1813246471227 | | 1992 | 4.4270323212537 |
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