Year Number 2004-01-01 29.2871 2005-01-01 29.3714 2006-01-01 29.4992 2007-01-01 29.4724 2008-01-01 29.6802 2009-01-01 29.5876 2010-01-01 30.3000 2011-01-01 29.1173 2012-01-01 31.2582 2013-01-01 31.1281 2014-01-01 30.8787 2015-01-01 30.9099 2016-01-01 30.9382