Year Number 2004-01-01 11.73032408 2005-01-01 13.90027668 2006-01-01 12.72476991 2007-01-01 10.28694585 2008-01-01 13.19858554 2009-01-01 14.55529463 2010-01-01 16.65543135 2011-01-01 18.85176830 2012-01-01 20.38697648 2013-01-01 15.97550394