Year	Number
2004-01-01	6
2005-01-01	6
2006-01-01	6
2007-01-01	6
2008-01-01	8
2009-01-01	8
2010-01-01	8
2011-01-01	9
2012-01-01	9
2013-01-01	9
2014-01-01	11
2015-01-01	12
2016-01-01	11
2017-01-01	11