Year	Number
2004-01-01	12
2005-01-01	17
2006-01-01	18
2007-01-01	17
2008-01-01	16
2009-01-01	18
2010-01-01	19
2011-01-01	19
2012-01-01	19
2013-01-01	21
2014-01-01	21
2015-01-01	24
2016-01-01	24