Year | Value | 2020 | 15.042193562444 | 2017 | 17.389828491841 | 2016 | 18.344461438908 | 2015 | 19.639159897367 | 2014 | 18.452720949661 | 2013 | 17.833057048454 | 2012 | 17.904545183148 | 2011 | 18.075171712773 | 2010 | 16.311766426322 | 2009 | 18.868962404117 | 2008 | 20.036635801331 | 2007 | 21.63213001123 | 2006 | 20.850042243322 | 2005 | 20.661813327016 | 2004 | 21.254758408043 | 2003 | 21.503968817561 | 2002 | 21.025038339717 | 2001 | 15.730337078652 | 2000 | 16.52834435223 | 1994 | 15.246006550136 | 1993 | 15.197854354481 | 1992 | 14.523456261376 | 1991 | 14.585362576831 | 1990 | 14.386293897034 |
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