Year Number 2005-01-01 12.9427 2006-01-01 14.0529 2007-01-01 15.3202 2008-01-01 17.1564 2009-01-01 17.3352 2010-01-01 17.8761 2011-01-01 18.2380 2012-01-01 18.6219 2013-01-01 19.6709 2014-01-01 19.6373 2015-01-01 19.1993 2016-01-01 18.1398 2017-01-01 17.7391