Year	Number
2004-01-01	16
2005-01-01	19
2006-01-01	18
2007-01-01	22
2008-01-01	23
2009-01-01	24
2010-01-01	26
2011-01-01	26
2012-01-01	26
2013-01-01	26
2014-01-01	26
2015-01-01	31
2016-01-01	27
2017-01-01	25