Year Number 2004-01-01 23.7991 2005-01-01 23.8330 2006-01-01 23.8427 2007-01-01 23.0215 2008-01-01 22.7086 2009-01-01 22.7572 2010-01-01 20.7541 2011-01-01 20.5670 2012-01-01 20.1635 2013-01-01 19.3618 2014-01-01 18.5011 2015-01-01 17.1108 2016-01-01 14.6278