Quarter	Percent
2006-01-01	55.1
2006-04-01	58.4
2006-07-01	58.6
2006-10-01	57.6
2007-01-01	56
2007-04-01	58.7
2007-07-01	58.6
2007-10-01	56.8
2008-01-01	56
2008-04-01	59.2
2008-07-01	59.4
2008-10-01	58.4
2009-01-01	57.3
2009-04-01	60.1
2009-07-01	60.5
2009-10-01	59.8
2010-01-01	59.7
2010-04-01	62.1
2010-07-01	61.5
2010-10-01	61
2011-01-01	61
2011-04-01	63.3
2011-07-01	62.9
2011-10-01	62
2012-01-01	60.9
2012-04-01	63.5
2012-07-01	63.2
2012-10-01	63.7
2013-01-01	62.9
2013-04-01	65.1
2013-07-01	63.9
2013-10-01	64
2014-01-01	63.4
2014-04-01	65
2014-07-01	64.6
2014-10-01	64.7
2015-01-01	64.6
2015-04-01	66.0
2015-07-01	65.5
2015-10-01	65.7
2016-01-01	65.4
2016-04-01	66.9
2016-07-01	66.7
2016-10-01	66.9
2017-01-01	66.8
2017-04-01	67.9
2017-07-01	67.7
2017-10-01	67.7
2018-01-01	67.3
2018-04-01	68.1