Year	Number
2004-01-01	1
2005-01-01	1
2006-01-01	1
2007-01-01	1
2008-01-01	2
2009-01-01	2
2010-01-01	2
2011-01-01	4
2012-01-01	4
2013-01-01	5
2014-01-01	5
2015-01-01	4
2016-01-01	4
2017-01-01	4