Year	Number
2004-01-01	21022836
2005-01-01	20757864
2006-01-01	20470147
2007-01-01	20050696
2008-01-01	19903622
2009-01-01	19620713
2010-01-01	19060480
2011-01-01	18991523
2012-01-01	18882808
2013-01-01	19343621
2014-01-01	20908751
2015-01-01	21627389
2016-01-01	22351237
2017-01-01	23036318