| Year | Value | | 2022 | 6.0812811411241 | | 2021 | 3.6169053010881 | | 2020 | 2.2093823693347 | | 2019 | 3.7223941442269 | | 2018 | 4.2915910533787 | | 2017 | 6.1457998111116 | | 2016 | 6.7285823459334 | | 2015 | 3.3940153841056 | | 2014 | 5.350169668596 | | 2013 | 5.600925022904 | | 2012 | 6.7219977733489 | | 2011 | 5.005595180812 | | 2010 | 4.8749198764395 | | 2009 | 9.4517265152171 | | 2008 | 9.0946430719281 | | 2007 | 6.5478814110172 | | 2006 | 4.9611668929892 | | 2005 | 2.2819460702431 | | 2004 | 4.1366321314475 | | 2003 | 7.1361531145863 |
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