Year	Number
2004-01-01	20
2005-01-01	20
2006-01-01	21
2007-01-01	23
2008-01-01	23
2009-01-01	23
2010-01-01	25
2011-01-01	26
2012-01-01	29
2013-01-01	30
2014-01-01	32
2015-01-01	31