Year	Percent
2004-01-01	13.8
2005-01-01	13.7
2006-01-01	12.9
2007-01-01	12.5
2008-01-01	13.9
2009-01-01	18.6
2010-01-01	18.8
2011-01-01	17.6
2012-01-01	17.5
2013-01-01	17.0
2014-01-01	15.4
2015-01-01	14.0
2016-01-01	12.9