Year Number 2007-01-01 6.9814 2008-01-01 7.4791 2009-01-01 7.6002 2010-01-01 7.8827 2011-01-01 8.0307 2012-01-01 8.0576 2013-01-01 8.7167 2014-01-01 9.0395 2015-01-01 9.0934 2016-01-01 9.1875 2017-01-01 8.9185