Year Number 2006-01-01 12.7967 2007-01-01 15.2475 2008-01-01 20.0364 2009-01-01 22.2953 2010-01-01 28.0190 2011-01-01 31.7002 2012-01-01 36.2369 2013-01-01 43.0592 2014-01-01 44.9511 2015-01-01 47.9153