| Year | Value | | 2022 | 27.208288381465 | | 2021 | 11.873958884023 | | 2020 | 13.446871110105 | | 2019 | 14.804999090602 | | 2018 | 16.02954476937 | | 2017 | 18.221509400339 | | 2016 | 10.88606094139 | | 2015 | 6.6894356249868 | | 2014 | 4.6393117140967 | | 2013 | 5.5241287799427 | | 2012 | 6.5877623939258 | | 2011 | 6.7913829195262 | | 2010 | 7.1856627566816 | | 2009 | 7.4690189854098 | | 2008 | 8.2111243228961 | | 2007 | 11.649974451811 |
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