Year	Number
2004-01-01	23
2005-01-01	21
2006-01-01	18
2007-01-01	18
2008-01-01	18
2009-01-01	18
2010-01-01	18
2011-01-01	22
2012-01-01	22
2013-01-01	23
2014-01-01	25
2015-01-01	25
2016-01-01	27