Quarter	Percent
2006-01-01	44.9
2006-04-01	41.6
2006-07-01	41.4
2006-10-01	42.4
2007-01-01	44
2007-04-01	41.3
2007-07-01	41.4
2007-10-01	43.2
2008-01-01	44
2008-04-01	40.8
2008-07-01	40.6
2008-10-01	41.6
2009-01-01	42.7
2009-04-01	39.9
2009-07-01	39.5
2009-10-01	40.2
2010-01-01	40.3
2010-04-01	37.9
2010-07-01	38.5
2010-10-01	39
2011-01-01	39
2011-04-01	36.7
2011-07-01	37.1
2011-10-01	38
2012-01-01	39.1
2012-04-01	36.5
2012-07-01	36.8
2012-10-01	36.3
2013-01-01	37.1
2013-04-01	34.9
2013-07-01	36.1
2013-10-01	36
2014-01-01	36.6
2014-04-01	35
2014-07-01	35.4
2014-10-01	35.3
2015-01-01	35.4
2015-04-01	34.0
2015-07-01	34.5
2015-10-01	34.3
2016-01-01	34.6
2016-04-01	33.1
2016-07-01	33.3
2016-10-01	33.1
2017-01-01	33.2
2017-04-01	32.1
2017-07-01	32.3
2017-10-01	32.3
2018-01-01	32.7
2018-04-01	31.9