Year	Number
2004-01-01	3.7133
2005-01-01	3.8641
2006-01-01	3.8719
2007-01-01	3.8573
2008-01-01	3.7373
2009-01-01	3.2207
2010-01-01	2.3280
2011-01-01	1.6037
2012-01-01	1.0719
2013-01-01	0.9190
2014-01-01	0.7674
2015-01-01	0.5632
2016-01-01	0.4954
2017-01-01	0.4509