Year Number 2008-01-01 3.8303 2009-01-01 3.9221 2010-01-01 4.0683 2011-01-01 4.3889 2012-01-01 4.5401 2013-01-01 4.6372 2014-01-01 4.6431 2015-01-01 4.3416 2016-01-01 4.5502 2017-01-01 4.7213