Year Number 2004 4436000 2005 4481000 2006 4533000 2007 4928000 2008 5425000 2009 5793000 2010 6083000 2011 7676000 2012 8295000 2013 9844000 2014 10022000 2015 13159000 2016 18645000 2017 21583000 2018 18411000 2019 15352000