Year	Number
2004-01-01	4
2005-01-01	6
2006-01-01	6
2007-01-01	7
2008-01-01	8
2009-01-01	8
2010-01-01	8
2011-01-01	8
2012-01-01	8
2013-01-01	8
2014-01-01	7
2015-01-01	7
2016-01-01	6
2017-01-01	6