Year | Value | 2021 | 0.5 | 2020 | 0.4 | 2019 | 0.4 | 2018 | 0.1 | 2017 | 0.1 | 2016 | 0.3 | 2015 | 0.3 | 2014 | 0.2 | 2013 | 0.2 | 2012 | 0.3 | 2011 | 0.2 | 2010 | 0.3 | 2009 | 0.4 | 2008 | 0.1 | 2007 | 0.1 | 2006 | 0.2 | 2005 | 0.3 | 2004 | 0.3 | 2003 | 0.4 | 2002 | 0.2 | 2001 | 0.2 | 2000 | 0.5 | 1999 | 0.5 | 1998 | 0.5 | 1997 | 0.5 | 1996 | 0.7 | 1990 | 0.5 | 1984 | 1.2 | 1979 | 1.2 | 1975 | 2.5 | 1970 | 4 |
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