| Year | Value | | 2022 | 40.927840939481 | | 2021 | 36.80613939445 | | 2020 | 31.295880224427 | | 2019 | 34.922262523285 | | 2018 | 35.816867650947 | | 2017 | 34.496421142303 | | 2016 | 32.314098901232 | | 2015 | 34.029299141746 | | 2014 | 39.306097253623 | | 2013 | 40.597172611646 | | 2012 | 42.239395897449 | | 2011 | 41.659605662703 |
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