Year Number 2000 16.95893 2001 17.31881 2002 17.48617 2003 17.09607 2004 16.33875 2005 16.16185 2006 15.87323 2007 16.32016 2008 15.25295 2009 13.0384 2010 11.58301 2011 12.34803 2012 12.68218 2013 11.51109