Year Number 2007-01-01 9281.0 2008-01-01 15521.0 2009-01-01 17828.0 2010-01-01 20704.0 2011-01-01 23315.0 2012-01-01 29376.0 2013-01-01 24740.0 2014-01-01 22421.0 2015-01-01 15809.0 2016-01-01 17249.1