| Year | Value | | 2022 | 10.467424446599 | | 2021 | 4.9284139694897 | | 2020 | 3.6818134162557 | | 2019 | 5.3762899084413 | | 2018 | 4.9472372803989 | | 2017 | 3.8506716628473 | | 2016 | 3.5231731762847 | | 2015 | 3.997379966944 | | 2014 | 6.0359686179842 | | 2013 | 7.1354678528941 | | 2012 | 7.1935505333896 | | 2011 | 8.082387980991 | | 2010 | 5.4551342588742 | | 2009 | 3.687001604988 | | 2008 | 19.826203128743 | | 2007 | 11.126934744612 | | 2006 | 9.1401996677772 | | 2005 | 9.5990998606442 | | 2004 | 8.4702106358408 | | 2003 | 5.3023877321994 | | 2002 | 3.7501746577847 | | 2001 | 5.9860418627952 | | 2000 | 7.0699135225252 |
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