Year	Number
2004-01-01	14
2005-01-01	16
2006-01-01	18
2007-01-01	19
2008-01-01	19
2009-01-01	20
2010-01-01	20
2011-01-01	22
2012-01-01	25
2013-01-01	27
2014-01-01	29
2015-01-01	29
2016-01-01	29
2017-01-01	32