Quarter	Percent
1999-04-01	23.5
2000-04-01	23
2001-04-01	22.5
2002-04-01	22
2003-04-01	21.2
2004-04-01	21.2
2005-01-01	20.7
2005-04-01	20.9
2005-07-01	21.1
2005-10-01	20.9
2006-01-01	19.7
2006-04-01	19.7
2006-07-01	19.7
2006-10-01	19.8
2007-01-01	19.4
2007-04-01	19.7
2007-07-01	19.3
2007-10-01	19.2
2008-01-01	19.7
2008-04-01	19.8
2008-07-01	19.4
2008-10-01	19.1
2009-01-01	19.6
2009-04-01	19.2
2009-07-01	19
2009-10-01	18.3
2010-01-01	19.1
2010-04-01	18.5
2010-07-01	18.8
2010-10-01	18.3
2011-01-01	18.4
2011-04-01	17.9
2011-07-01	17.7
2011-10-01	17.4
2012-01-01	18
2012-04-01	17.7
2012-07-01	17.9
2012-10-01	17.4
2013-01-01	17.6
2013-04-01	17.3
2013-07-01	17.5
2013-10-01	17.8
2014-01-01	17.7
2014-04-01	17.3
2014-07-01	17.5
2014-10-01	17.6
2015-01-01	17.5
2015-04-01	17.2
2015-07-01	17.8
2015-10-01	17.5
2016-01-01	17.5
2016-04-01	17.7
2016-07-01	17.3
2016-10-01	17.0
2017-01-01	17.6
2017-04-01	17.9
2017-07-01	17.4
2017-10-01	17.0
2018-01-01	17.3
2018-04-01	17.4