Year	Number
2004-01-01	18475652
2005-01-01	18276462
2006-01-01	18066795
2007-01-01	17662909
2008-01-01	17553145
2009-01-01	17316850
2010-01-01	16780776
2011-01-01	16784293
2012-01-01	16748862
2013-01-01	17262129
2014-01-01	18842721
2015-01-01	19577436
2016-01-01	20286468
2017-01-01	20965896