Quarter	Percent
1998-04-01	41.8
1999-04-01	41.8
2000-04-01	42.4
2001-04-01	41.2
2002-04-01	40.7
2003-04-01	40.5
2004-04-01	40.9
2005-04-01	40.7
2006-04-01	40.2
2007-04-01	40.1
2008-04-01	38.7
2009-04-01	38.4
2010-01-01	40.0
2010-04-01	40.2
2010-07-01	39.8
2010-10-01	40.1
2011-01-01	39.6
2011-04-01	39.6
2011-07-01	39.6
2011-10-01	39.0
2012-01-01	39.2
2012-04-01	39.3
2012-07-01	38.9
2012-10-01	39.3
2013-01-01	39.0
2013-04-01	39.0
2013-07-01	38.8
2013-10-01	38.6
2014-01-01	38.8
2014-04-01	38.4
2014-07-01	38.1
2014-10-01	37.1
2015-01-01	37.8
2015-04-01	38.0
2015-07-01	37.8
2015-10-01	37.2
2016-01-01	36.9
2016-04-01	37.4
2016-07-01	37.4
2016-10-01	37.0
2017-01-01	37.1
2017-04-01	37.6
2017-07-01	37.5
2017-10-01	37.4
2018-01-01	37.0
2018-04-01	37.4