Year	Number
2004-01-01	7
2005-01-01	7
2006-01-01	9
2007-01-01	11
2008-01-01	16
2009-01-01	16
2010-01-01	18
2011-01-01	18
2012-01-01	17
2013-01-01	17
2014-01-01	16
2015-01-01	17
2016-01-01	17
2017-01-01	17