Year | Value | 2021 | 19.837 | 2020 | 19.213 | 2019 | 16.801 | 2018 | 18.257 | 2017 | 18.12 | 2016 | 15.275 | 2015 | 13.075 | 2014 | 11.9 | 2013 | 12.6 | 2012 | 12.2 | 2011 | 12.9 | 2010 | 12.5 | 2009 | 12.9 | 2008 | 12.7 | 2007 | 13.1 | 2006 | 14 | 2005 | 14.8 | 2003 | 14.5 | 2002 | 15.3 | 2001 | 14.7 | 2000 | 13.7 | 1996 | 13.7 | 1995 | 14.6 | 1993 | 19.7 | 1987 | 14.8 | 1986 | 13.3 | 1983 | 6.6 |
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