Year	Number
2004-01-01	5
2005-01-01	7
2006-01-01	8
2007-01-01	8
2008-01-01	8
2009-01-01	8
2010-01-01	8
2011-01-01	8
2012-01-01	10
2013-01-01	13
2014-01-01	14
2015-01-01	14
2016-01-01	15
2017-01-01	16