Year	Number
2004-01-01	7
2005-01-01	7
2006-01-01	6
2007-01-01	6
2008-01-01	7
2009-01-01	13
2010-01-01	16
2011-01-01	18
2012-01-01	20
2013-01-01	20
2014-01-01	22
2015-01-01	21
2016-01-01	21