Year	Number
2004-01-01	7
2005-01-01	7
2006-01-01	8
2007-01-01	9
2008-01-01	11
2009-01-01	13
2010-01-01	15
2011-01-01	15
2012-01-01	15
2013-01-01	15
2014-01-01	14
2015-01-01	15