Quarter	Percent
1998-04-01	47.6
1999-04-01	47.5
2000-04-01	48.7
2001-04-01	45.5
2002-04-01	46.8
2003-04-01	44.6
2004-04-01	44
2005-04-01	42.3
2006-04-01	41.4
2007-04-01	39.7
2008-04-01	38.4
2009-04-01	39
2010-01-01	40.3
2010-04-01	40.7
2010-07-01	42.1
2010-10-01	40.9
2011-01-01	39.5
2011-04-01	39.2
2011-07-01	40.2
2011-10-01	38.7
2012-01-01	38.6
2012-04-01	37.4
2012-07-01	38.0
2012-10-01	38.6
2013-01-01	36.9
2013-04-01	35.6
2013-07-01	36.9
2013-10-01	37.6
2014-01-01	37.0
2014-04-01	34.8
2014-07-01	35.9
2014-10-01	35.8
2015-01-01	34.8
2015-04-01	34.3
2015-07-01	33.3
2015-10-01	32.6
2016-01-01	32.3
2016-04-01	31.5
2016-07-01	32.5
2016-10-01	32.0
2017-01-01	33.2
2017-04-01	32.1
2017-07-01	31.8
2017-10-01	30.8
2018-01-01	30.8
2018-04-01	30.9