Quarter	Percent
2005-01-01	19.8
2005-04-01	19.4
2005-07-01	19.4
2005-10-01	19.3
2006-01-01	19.5
2006-04-01	19.1
2006-07-01	19.1
2006-10-01	19.0
2007-01-01	19.3
2007-04-01	18.9
2007-07-01	19.0
2007-10-01	18.8
2008-01-01	19.1
2008-04-01	18.7
2008-07-01	18.8
2008-10-01	18.7
2009-01-01	19.0
2009-04-01	18.7
2009-07-01	18.8
2009-10-01	18.7
2010-01-01	18.9
2010-04-01	18.5
2010-07-01	18.8
2010-10-01	18.8
2011-01-01	19.0
2011-04-01	18.6
2011-07-01	18.8
2011-10-01	18.6
2012-01-01	18.9
2012-04-01	18.4
2012-07-01	18.5
2012-10-01	18.4
2013-01-01	18.8
2013-04-01	18.3
2013-07-01	18.6
2013-10-01	18.5
2014-01-01	18.6
2014-04-01	18.4
2014-07-01	18.6
2014-10-01	18.4
2015-01-01	18.6
2015-04-01	18.3
2015-07-01	18.5
2015-10-01	18.2
2016-01-01	18.3
2016-04-01	18.1
2016-07-01	18.1
2016-10-01	18.0
2017-01-01	18.1
2017-04-01	17.8