Year	Number
2007-01-01	3
2008-01-01	4
2009-01-01	5
2010-01-01	5
2011-01-01	5
2012-01-01	5
2013-01-01	6
2014-01-01	6
2015-01-01	7
2016-01-01	7
2017-01-01	5