Year Number 2008-01-01 18688 2009-01-01 33879 2010-01-01 85043 2011-01-01 257110 2012-01-01 446183 2013-01-01 539755 2014-01-01 549582 2015-01-01 601668 2016-01-01 694646 2017-01-01 735945