Year	Number
2004-01-01	2
2005-01-01	3
2006-01-01	4
2007-01-01	4
2008-01-01	4
2009-01-01	3
2010-01-01	2
2011-01-01	2
2012-01-01	2
2013-01-01	2
2014-01-01	2
2015-01-01	3
2016-01-01	3