Quarter	Percent
1999-01-01	11.6
2000-01-01	15.3
2000-04-01	14.6
2000-07-01	13.7
2000-10-01	14.2
2001-01-01	17
2001-04-01	17
2001-07-01	16.4
2001-10-01	17.3
2002-01-01	19.7
2002-04-01	19.3
2002-07-01	18.6
2002-10-01	19.1
2003-01-01	20.3
2003-04-01	18.9
2003-07-01	18.3
2003-10-01	18.4
2004-01-01	20.2
2004-04-01	18.5
2004-07-01	17.5
2004-10-01	16.7
2005-01-01	17.9
2005-04-01	17.2
2005-07-01	16
2005-10-01	15.5
2006-01-01	15.5
2006-04-01	13.4
2006-07-01	12
2006-10-01	11
2007-01-01	10.7
2007-04-01	9.2
2007-07-01	8.4
2007-10-01	7.8
2008-01-01	7.6
2008-04-01	6.6
2008-07-01	5.7
2008-10-01	6.0
2009-01-01	7.8
2009-04-01	7.5
2009-07-01	7.6
2009-10-01	8.2
2010-01-01	10.6
2010-04-01	9.3
2010-07-01	8.7
2010-10-01	8.9
2011-01-01	10
2011-04-01	9.0
2011-07-01	8.3
2011-10-01	8.9
2012-01-01	10.2
2012-04-01	9.2
2012-07-01	9.0
2012-10-01	9.4
2013-01-01	10.8
2013-04-01	9.8
2013-07-01	9.0
2013-10-01	9.2
2014-01-01	10.3
2014-04-01	8.7
2014-07-01	7.5
2014-10-01	7.6
2015-01-01	8.5
2015-04-01	7.4
2015-07-01	6.7
2015-10-01	6.8
2016-01-01	7.0
2016-04-01	6.3
2016-07-01	5.7
2016-10-01	5.4
2017-01-01	5.4
2017-04-01	5.2
2017-07-01	4.6
2017-10-01	4.4
2018-01-01	4.1
2018-04-01	3.7