Year	Number
2004-01-01	12
2005-01-01	12
2006-01-01	11
2007-01-01	13
2008-01-01	17
2009-01-01	17
2010-01-01	17
2011-01-01	18
2012-01-01	18
2013-01-01	15
2014-01-01	15
2015-01-01	13
2016-01-01	13
2017-01-01	12