Year | Value | 2020 | 2.566 | 2019 | 1.749 | 2018 | 1.834 | 2017 | 1.987 | 2016 | 1.939 | 2015 | 1.81 | 2014 | 1.67 | 2013 | 1.82 | 2012 | 1.97 | 2011 | 2.56 | 2010 | 2.84 | 2009 | 3.58 | 2008 | 2.999 | 2007 | 3.27 | 2006 | 3.822 | 2005 | 4.158 | 2004 | 4.905 | 2003 | 5.995 | 2002 | 6.267 | 2001 | 6.393 | 2000 | 6.874 | 1999 | 6.348 | 1998 | 4.607 | 1997 | 3.261 | 1996 | 4.249 | 1995 | 3.581 | 1994 | 2.48 | 1993 | 2.057 | 1992 | 2.197 | 1991 | 3.01 |
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