Year Number 2004-01-01 2.8678 2005-01-01 3.2589 2006-01-01 4.2720 2007-01-01 3.8880 2008-01-01 4.1561 2009-01-01 4.6156 2010-01-01 6.4173 2011-01-01 7.0195 2012-01-01 11.8395 2013-01-01 12.2265 2014-01-01 13.8301 2015-01-01 15.1070