Quarter	Percent
1999-01-01	12.3
2000-01-01	16.8
2000-04-01	16.4
2000-07-01	15.4
2000-10-01	16
2001-01-01	18.3
2001-04-01	18.4
2001-07-01	17.9
2001-10-01	18.5
2002-01-01	20.3
2002-04-01	20
2002-07-01	19.9
2002-10-01	19.8
2003-01-01	20.6
2003-04-01	19.4
2003-07-01	19.4
2003-10-01	19.3
2004-01-01	20.7
2004-04-01	19.1
2004-07-01	18.2
2004-10-01	18
2005-01-01	18.9
2005-04-01	18.1
2005-07-01	17.4
2005-10-01	16.8
2006-01-01	16.1
2006-04-01	14.1
2006-07-01	13.1
2006-10-01	12.2
2007-01-01	11.3
2007-04-01	9.6
2007-07-01	9.0
2007-10-01	8.5
2008-01-01	8.1
2008-04-01	7.1
2008-07-01	6.6
2008-10-01	6.7
2009-01-01	8.3
2009-04-01	7.9
2009-07-01	8.1
2009-10-01	8.5
2010-01-01	10.6
2010-04-01	9.6
2010-07-01	9.2
2010-10-01	9.3
2011-01-01	10.1
2011-04-01	9.5
2011-07-01	9.3
2011-10-01	9.8
2012-01-01	10.5
2012-04-01	9.9
2012-07-01	9.9
2012-10-01	10.1
2013-01-01	11.3
2013-04-01	10.5
2013-07-01	9.8
2013-10-01	9.8
2014-01-01	10.6
2014-04-01	9.1
2014-07-01	8.2
2014-10-01	8.1
2015-01-01	8.6
2015-04-01	7.4
2015-07-01	7.1
2015-10-01	6.9
2016-01-01	7.0
2016-04-01	6.2
2016-07-01	5.9
2016-10-01	5.6
2017-01-01	5.4
2017-04-01	5.0
2017-07-01	4.7
2017-10-01	4.5
2018-01-01	4.2
2018-04-01	3.6