Year | Value | 2021 | 28.690138416751 | 2020 | 30.923781870195 | 2019 | 24.640415741758 | 2018 | 23.112732557208 | 2017 | 23.572490908899 | 2016 | 22.812412998135 | 2015 | 21.928524296887 | 2014 | 20.533849699661 | 2013 | 18.166595249635 | 2012 | 19.469901278012 | 2011 | 20.094896528291 | 2010 | 20.993813300737 | 2009 | 22.389435297014 | 2008 | 18.000869514923 | 1998 | 100.41058329933 |
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