Year | Value | 2021 | 12.2 | 2020 | 13.2 | 2019 | 13.1 | 2018 | 15.6 | 2017 | 15.1 | 2016 | 15.7 | 2015 | 14.6 | 2014 | 18.7 | 2013 | 19.5 | 2012 | 22.5 | 2011 | 22.9 | 2010 | 27.4 | 2009 | 29.8 | 2008 | 32.7 | 2007 | 34.8 | 2006 | 36.9 | 2004 | 44.3 | 2002 | 50.8 | 2000 | 59 | 1999 | 58.3 | 1998 | 54.1 | 1996 | 56.1 | 1994 | 60.4 | 1992 | 66.1 | 1990 | 72.6 | 1988 | 76.2 | 1981 | 76.9 |
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