Quarter	Percent
1998-04-01	19.0
1999-04-01	19
2000-04-01	19.5
2001-04-01	18.8
2002-04-01	18.7
2003-04-01	18.7
2004-04-01	19
2005-04-01	19.1
2006-04-01	18.8
2007-04-01	18.4
2008-04-01	17.7
2009-04-01	17.5
2010-01-01	18.9
2010-04-01	18.9
2010-07-01	18.3
2010-10-01	18.8
2011-01-01	18.1
2011-04-01	18.2
2011-07-01	17.8
2011-10-01	17.6
2012-01-01	18.0
2012-04-01	18.1
2012-07-01	17.1
2012-10-01	17.6
2013-01-01	17.7
2013-04-01	17.9
2013-07-01	17.5
2013-10-01	17.3
2014-01-01	17.6
2014-04-01	17.4
2014-07-01	17.0
2014-10-01	16.4
2015-01-01	16.8
2015-04-01	17.1
2015-07-01	16.8
2015-10-01	16.1
2016-01-01	15.9
2016-04-01	16.6
2016-07-01	16.2
2016-10-01	15.8
2017-01-01	16.2
2017-04-01	16.4
2017-07-01	15.8
2017-10-01	15.8
2018-01-01	16.0
2018-04-01	16.1