Quarter	Percent
1998-04-01	18.3
1999-04-01	19.1
2000-04-01	20.7
2001-04-01	17.5
2002-04-01	21.1
2003-04-01	20.3
2004-04-01	20.9
2005-04-01	22.2
2006-04-01	22.9
2007-04-01	21.6
2008-04-01	21.1
2009-04-01	20.5
2010-01-01	22.1
2010-04-01	21.5
2010-07-01	21.6
2010-10-01	21.4
2011-01-01	21.0
2011-04-01	20.9
2011-07-01	20.6
2011-10-01	20.4
2012-01-01	21.4
2012-04-01	21.2
2012-07-01	19.8
2012-10-01	19.9
2013-01-01	20.3
2013-04-01	20.2
2013-07-01	20.3
2013-10-01	19.3
2014-01-01	21.0
2014-04-01	21.5
2014-07-01	21.7
2014-10-01	19.3
2015-01-01	18.7
2015-04-01	20.2
2015-07-01	20.9
2015-10-01	19.4
2016-01-01	21.0
2016-04-01	19.2
2016-07-01	18.4
2016-10-01	18.6
2017-01-01	19.3
2017-04-01	17.8
2017-07-01	18.0
2017-10-01	16.8
2018-01-01	18.3
2018-04-01	16.2