Quarter	Percent
1999-01-01	24.7
2000-01-01	19
2001-01-01	16
2002-01-01	17.5
2003-01-01	16.5
2003-04-01	16.3
2003-07-01	18
2003-10-01	20.4
2004-01-01	19.7
2004-04-01	17.5
2004-07-01	19.1
2004-10-01	20.5
2005-01-01	20.1
2005-04-01	17.7
2005-07-01	19.4
2005-10-01	20.6
2006-01-01	21.7
2006-04-01	19.4
2006-07-01	18.4
2006-10-01	22.2
2007-01-01	19.6
2007-04-01	17.7
2007-07-01	17.4
2007-10-01	18.6
2008-01-01	17.3
2008-04-01	17.1
2008-07-01	18.2
2008-10-01	21.5
2009-01-01	23.6
2009-04-01	23.6
2009-07-01	23.1
2009-10-01	25.9
2010-01-01	24.3
2010-04-01	21.1
2010-07-01	21.7
2010-10-01	21.6
2011-01-01	21.8
2011-04-01	20.8
2011-07-01	19.5
2011-10-01	23.4
2012-01-01	23.4
2012-04-01	22.8
2012-07-01	22.9
2012-10-01	27.1
2013-01-01	26.0
2013-04-01	23.0
2013-07-01	22.2
2013-10-01	24.0
2014-01-01	24.8
2014-04-01	24.2
2014-07-01	23.9
2014-10-01	27.7
2015-01-01	27.4
2015-04-01	23.5
2015-07-01	24.6
2015-10-01	27.7
2016-01-01	26.9
2016-04-01	23.2
2016-07-01	24.1
2016-10-01	26.1
2017-01-01	24.1
2017-04-01	22.5
2017-07-01	22.6
2017-10-01	23.4
2018-01-01	21.8
2018-04-01	20.6