Year | Value | 2021 | 1.9 | 2020 | 3.1 | 2019 | 2.8 | 2018 | 2.7 | 2017 | 2.5 | 2016 | 3.5 | 2015 | 3.5 | 2014 | 3.3 | 2013 | 3.8 | 2012 | 3.4 | 2011 | 3 | 2010 | 2.7 | 2009 | 2.3 | 2008 | 1.9 | 2007 | 1.6 | 2006 | 2.6 | 2005 | 2.6 | 2004 | 2.4 | 2003 | 2.2 | 2000 | 2.4 | 1999 | 2.5 | 1998 | 3 | 1997 | 4.5 | 1996 | 5.7 | 1995 | 4.7 | 1994 | 4.5 | 1993 | 4.5 | 1990 | 3 | 1985 | 7.2 | 1980 | 7.2 |
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