| Year | Value | | 2022 | 1.25 | | 2021 | 1.3 | | 2019 | 1.12 | | 2018 | 1.03 | | 2017 | 0.94 | | 2016 | 1.01 | | 2015 | 1.01 | | 2014 | 1.08 | | 2013 | 1.18 | | 2012 | 1.31 | | 2011 | 1.22 | | 2010 | 1.22 | | 2009 | 1.27 | | 2008 | 1.43 | | 2007 | 1.68 | | 2006 | 2.2 | | 2005 | 2.01 | | 2004 | 2 | | 2003 | 1.97 | | 2002 | 2.05 | | 2001 | 2.12 | | 2000 | 2.08 | | 1997 | 1.6499999762 | | 1989 | 2.3002998828888 | | 1981 | 2.9395999908447 |
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