Year | Value | 2023 | 30.8 | 2022 | 30.9 | 2021 | 33.5 | 2020 | 36 | 2019 | 30.6 | 2018 | 28.9 | 2017 | 28.3 | 2016 | 29.3 | 2015 | 29.8 | 2014 | 28.7 | 2013 | 32.5 | 2012 | 32.6 | 2011 | 35.9 | 2010 | 39.7 | 2009 | 44.4 | 2008 | 43.4 | 2007 | 45.9 | 2006 | 46.8 | 2005 | 51.9 | 2004 | 59.7 | 2003 | 58.7 | 2000 | 76.6 | 1999 | 68.6 | 1998 | 65 | 1995 | 65.3 | 1994 | 65.9 | 1987 | 60.8 |
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