| Year | Value | | 2021 | 9.834 | | 2020 | 9.475 | | 2019 | 8.194 | | 2018 | 8.799 | | 2017 | 9.5 | | 2016 | 9.35 | | 2015 | 9.14 | | 2014 | 9.27 | | 2013 | 7.17 | | 2012 | 7.529 | | 2011 | 7.851 | | 2010 | 8.1 | | 2009 | 8.84 | | 2008 | 6.363 | | 2007 | 6.351 | | 2006 | 6.81 | | 2005 | 7.18 | | 2004 | 8.59 | | 2003 | 9.057 | | 2002 | 10.136 | | 2001 | 11.061 | | 2000 | 11.707 | | 1999 | 11.864 | | 1998 | 11.32 | | 1997 | 8.93 | | 1996 | 7.65 | | 1995 | 5.62 |
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