Year	Number
2004-01-01	3
2005-01-01	12
2006-01-01	12
2007-01-01	15
2008-01-01	16
2009-01-01	16
2010-01-01	16
2011-01-01	11
2012-01-01	5
2013-01-01	4
2014-01-01	4
2015-01-01	4
2016-01-01	4
2017-01-01	4