Year	Number
2004-01-01	12
2005-01-01	12
2006-01-01	13
2007-01-01	14
2008-01-01	13
2009-01-01	14
2010-01-01	14
2011-01-01	14
2012-01-01	14
2013-01-01	15
2014-01-01	18
2015-01-01	19
2016-01-01	21
2017-01-01	20