Year	Number
2004-01-01	10
2005-01-01	10
2006-01-01	9
2007-01-01	12
2008-01-01	12
2009-01-01	12
2010-01-01	13
2011-01-01	15
2012-01-01	17
2013-01-01	17
2014-01-01	16
2015-01-01	16
2016-01-01	17
2017-01-01	16