Year Number 2008-01-01 3.9991 2009-01-01 4.0604 2010-01-01 4.0892 2011-01-01 4.4561 2012-01-01 4.6192 2013-01-01 4.8869 2014-01-01 4.9653 2015-01-01 5.2357 2016-01-01 5.2609 2017-01-01 5.1798