Quarter	Percent
1999-01-01	23.4
1999-04-01	23
1999-07-01	22.6
1999-10-01	22.7
2000-01-01	23.2
2000-04-01	22.7
2000-07-01	22.4
2000-10-01	22.4
2001-01-01	22.9
2001-04-01	22.9
2001-07-01	22.7
2001-10-01	23.2
2002-01-01	23.3
2002-04-01	23
2002-07-01	22.7
2002-10-01	23
2003-01-01	23.1
2003-04-01	22.1
2003-07-01	21.7
2003-10-01	21.8
2004-01-01	22.4
2004-04-01	22.2
2004-07-01	22
2004-10-01	22
2005-01-01	22.1
2005-04-01	21.4
2005-07-01	20.7
2005-10-01	20.9
2006-01-01	20.7
2006-04-01	20
2006-07-01	19.9
2006-10-01	19.7
2007-01-01	20.3
2007-04-01	19.9
2007-07-01	19.6
2007-10-01	19.6
2008-01-01	20.2
2008-04-01	19.8
2008-07-01	19.2
2008-10-01	19.6
2009-01-01	20
2009-04-01	19.7
2009-07-01	19.6
2009-10-01	19.6
2010-01-01	19.4
2010-04-01	19
2010-07-01	18.8
2010-10-01	19.3
2011-01-01	19.7
2011-04-01	18.7
2011-07-01	18.4
2011-10-01	18.2
2012-01-01	17.9
2012-04-01	17.2
2012-07-01	16.6
2012-10-01	16.8
2013-01-01	17.6
2013-04-01	16.6
2013-07-01	16.3
2013-10-01	16.3
2014-01-01	15.5
2014-04-01	15.1
2014-07-01	14.6
2014-10-01	14.8
2015-01-01	14.6
2015-04-01	14.2
2015-07-01	13.9
2015-10-01	14.1
2016-01-01	14.4
2016-04-01	13.8
2016-07-01	13.6
2016-10-01	13.7
2017-01-01	13.8
2017-04-01	13.1
2017-07-01	12.8
2017-10-01	13.0
2018-01-01	13.0
2018-04-01	12.6