Year	Percent
2005-01-01	19.5
2006-01-01	19.2
2007-01-01	19.0
2008-01-01	18.8
2009-01-01	18.8
2010-01-01	18.8
2011-01-01	18.7
2012-01-01	18.6
2013-01-01	18.5
2014-01-01	18.5
2015-01-01	18.4
2016-01-01	18.1