Year	Number
2004-01-01	11
2005-01-01	13
2006-01-01	14
2007-01-01	14
2008-01-01	14
2009-01-01	16
2010-01-01	16
2011-01-01	18
2012-01-01	18
2013-01-01	16
2014-01-01	14
2015-01-01	18
2016-01-01	18