Year Number 2008-01-01 2.6297 2009-01-01 4.8264 2010-01-01 8.6943 2011-01-01 10.8552 2012-01-01 12.9533 2013-01-01 17.9857 2014-01-01 19.9640 2015-01-01 23.2716 2016-01-01 24.2796 2017-01-01 26.6300