Year	Number
2004-01-01	2
2005-01-01	2
2006-01-01	2
2007-01-01	2
2008-01-01	2
2009-01-01	7
2010-01-01	7
2011-01-01	7
2012-01-01	9
2013-01-01	9
2014-01-01	9
2015-01-01	12
2016-01-01	13