Year | Value | 2019 | 11.466 | 2018 | 12.304 | 2017 | 13.616 | 2016 | 15.418 | 2015 | 17.193 | 2014 | 18.055 | 2013 | 15.866 | 2012 | 13.376 | 2011 | 13.481 | 2010 | 14.086 | 2009 | 13.674 | 2008 | 13.06 | 2007 | 15.966 | 2006 | 13.8 | 2005 | 6.566 | 2004 | 14.4 | 2003 | 15 | 2002 | 4.615 | 2001 | 16.4 | 2000 | 16.8 | 1999 | 18.4 | 1998 | 17.7 | 1997 | 14.9 | 1996 | 12.3 | 1995 | 12.9 | 1994 | 18.4 | 1993 | 22.3 | 1992 | 26.5 | 1991 | 9.1 | 1990 | 9.5 | 1989 | 7.3 | 1988 | 7 | 1987 | 6.1 | 1986 | 6.4 | 1985 | 6.7 | 1984 | 5.7 | 1983 | 4.4 | 1982 | 3.6 | 1981 | 5.1 | 1980 | 5.6 |
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