Year | Value | 2023 | 4.4 | 2021 | 4.3 | 2019 | 3.7 | 2018 | 4.4 | 2017 | 5.3 | 2016 | 5.8 | 2015 | 5.6 | 2014 | 7.4 | 2013 | 7 | 2012 | 8.7 | 2011 | 7.3 | 2010 | 9.1 | 2009 | 8 | 2008 | 10.5 | 2007 | 14.9 | 2006 | 17.4 | 2005 | 16.4 | 2004 | 17.6 | 2003 | 18.7 | 2002 | 19.5 | 2001 | 22.8 | 2000 | 18.3 | 1999 | 19.3 | 1998 | 21.6 | 1997 | 21.8 | 1995 | 22.7 | 1991 | 28.8 | 1989 | 31.8 | 1979 | 18.2 |
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