| Year | Value | | 2022 | 3.7412239185199 | | 2021 | 1.2374810283144 | | 2020 | 0.73533200109255 | | 2019 | 1.5801833363947 | | 2018 | 0.19510777373047 | | 2017 | 0.21257093422861 | | 2016 | 0.21910660490696 | | 2015 | 1.4316114581042 | | 2014 | 1.7329851003746 | | 2013 | 1.7243993362693 | | 2012 | 2.7790876828249 | | 2011 | 2.8772435849593 | | 2010 | 3.7491572759711 | | 2009 | 2.7539348508314 | | 2008 | 9.8899978869186 | | 2007 | 1.8597437935111 | | 2006 | 3.8423412562477 | | 2005 | 4.1072507071594 | | 2004 | 3.004174986386 | | 2003 | 4.4030322173088 | | 2002 | 5.7095158597663 | | 2001 | 1.222784758789 | | 2000 | 2.7981989243576 | | 1999 | 5.5443918036874 | | 1998 | 5.5796450583827 | | 1997 | 7.087005912057 |
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