Year Number 2005-01-01 2.7939 2006-01-01 2.8828 2007-01-01 3.0695 2008-01-01 3.2506 2009-01-01 3.3513 2010-01-01 3.4535 2011-01-01 3.5737 2012-01-01 3.6840 2013-01-01 3.7876 2014-01-01 3.9144 2015-01-01 4.0031 2016-01-01 3.9558 2017-01-01 4.2354