Year	Number
2004-01-01	18
2005-01-01	20
2006-01-01	21
2007-01-01	22
2008-01-01	22
2009-01-01	22
2010-01-01	25
2011-01-01	26
2012-01-01	24
2013-01-01	24
2014-01-01	24
2015-01-01	23
2016-01-01	24
2017-01-01	22