Year	Number
2004-01-01	20
2005-01-01	22
2006-01-01	22
2007-01-01	24
2008-01-01	21
2009-01-01	22
2010-01-01	22
2011-01-01	22
2012-01-01	20
2013-01-01	20
2014-01-01	21
2015-01-01	20
2016-01-01	16
2017-01-01	15