Year	Number
2006-01-01	1
2007-01-01	2
2008-01-01	2
2009-01-01	3
2010-01-01	3
2011-01-01	3
2012-01-01	3
2013-01-01	2
2014-01-01	2
2015-01-01	2
2016-01-01	2
2017-01-01	2