| Year | Value | | 2022 | 23.492331061256 | | 2021 | 21.879079042942 | | 2020 | 17.857490349675 | | 2019 | 20.14239541978 | | 2018 | 18.223926090045 | | 2017 | 15.597900002627 | | 2016 | 13.482575336056 | | 2015 | 11.747864262928 | | 2014 | 9.5527669313215 | | 2013 | 8.6579213826072 | | 2012 | 6.6445854619072 | | 2011 | 7.990085289407 | | 2010 | 8.6490274126398 | | 2009 | 9.4796850231447 | | 2008 | 11.450203606897 | | 2007 | 13.28057584322 | | 2006 | 10.844637336665 | | 2005 | 7.8434752474893 | | 2004 | 12.901952962685 | | 2003 | 3.6791190030456 | | 2002 | 6.492283394587 | | 2001 | 8.8808100571126 | | 2000 | 12.611739483323 |
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