| Year | Value | | 2016 | 17.638796165748 | | 2015 | 10.747365359808 | | 2014 | 10.171836708066 | | 2013 | 5.7172310685792 | | 2012 | 6.8680002433745 | | 2011 | 18.403077340036 | | 2010 | 9.6747163326298 | | 2009 | 16.621047697826 | | 2008 | 14.031316557675 | | 2007 | 19.139075254069 | | 2006 | 22.566044172648 | | 2005 | 20.244893262479 | | 2004 | 14.722405391226 | | 2003 | 10.564720185809 | | 2002 | 18.367605843903 | | 2001 | 1.3967128371383 | | 2000 | 8.5294610855397 | | 1988 | 0.61281468004534 | | 1987 | 4.7416785743651 | | 1986 | 4.5601232148504 | | 1985 | 3.4103253318662 | | 1984 | 4.9975610534246 |
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