Year | Value | 2020 | 19.61608145621 | 2019 | 16.193904309718 | 2018 | 15.230715144261 | 2017 | 14.680769175866 | 2016 | 15.804952313987 | 2015 | 19.086977673602 | 2014 | 18.325733607477 | 2013 | 19.016381288718 | 2012 | 20.623180785109 | 2011 | 21.074362282299 | 2010 | 21.886297052572 | 2009 | 19.251781868567 | 2008 | 8.0040299737667 | 2007 | 5.9431764131185 | 2006 | 6.023568086605 | 1996 | 11.156755549212 | 1995 | 10.972076070214 | 1994 | 12.042397635247 | 1993 | 12.445059946103 | 1992 | 12.53215057328 | 1991 | 12.116802057523 | 1990 | 11.371103249271 |
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