Year | Value | 2019 | 3.466 | 2018 | 3.383 | 2017 | 3.312 | 2016 | 3.197 | 2015 | 3.156 | 2014 | 3.105 | 2013 | 2.995 | 2012 | 2.949 | 2011 | 2.87 | 2010 | 2.816 | 2009 | 2.696 | 2008 | 2.686 | 2007 | 2.678 | 2006 | 2.547 | 2005 | 2.506 | 2004 | 2.497 | 2003 | 2.425 | 2002 | 2.362 | 2001 | 2.341 | 2000 | 2.295 | 1999 | 2.42 | 1998 | 2.504 | 1997 | 2.642 | 1996 | 2.62 | 1995 | 2.612 | 1994 | 2.649 | 1993 | 2.692 | 1992 | 2.68 | 1991 | 2.628 | 1990 | 2.91 | 1984 | 1.88 | 1983 | 1.858 | 1982 | 1.808 | 1981 | 1.738 | 1980 | 1.673 |
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