Year	Number
2004-01-01	16
2005-01-01	17
2006-01-01	20
2007-01-01	20
2008-01-01	23
2009-01-01	28
2010-01-01	27
2011-01-01	27
2012-01-01	25
2013-01-01	25
2014-01-01	25
2015-01-01	24
2016-01-01	24