Year Number 2006-01-01 24.5783 2007-01-01 24.6693 2008-01-01 24.6128 2009-01-01 24.1864 2010-01-01 24.0506 2011-01-01 24.1750 2012-01-01 24.2737 2013-01-01 24.1349 2014-01-01 23.9293 2015-01-01 23.6249 2016-01-01 22.9870 2017-01-01 21.7145