| Year | Value | | 2021 | 30.613034032682 | | 2020 | 43.113136105896 | | 2019 | 36.820224340194 | | 2018 | 39.155428984166 | | 2017 | 44.790385072137 | | 2014 | 41.707610126386 | | 2013 | 41.086815518466 | | 2012 | 47.718228127509 | | 2011 | 33.905898963457 | | 2010 | 30.269413242713 | | 2009 | 39.566115805553 | | 2008 | 37.890071745481 | | 2007 | 45.374891989501 | | 2006 | 41.525849613669 | | 1996 | 37.231523409912 | | 1995 | 37.722290444353 | | 1994 | 31.254939843681 | | 1993 | 34.467015706806 | | 1992 | 40.986904224311 | | 1991 | 37.386480781503 | | 1990 | 24.6541652273 |
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