Year | Value | 2021 | 13.782469423754 | 2020 | 12.940187657173 | 2019 | 13.227328858402 | 2018 | 13.208927664955 | 2017 | 13.13038609045 | 2016 | 13.414585170335 | 2015 | 13.393533434981 | 2014 | 12.852675293501 | 2013 | 12.885737374828 | 2012 | 12.799280967251 | 2011 | 13.125010919699 | 2010 | 12.681985009379 |
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