Quarter	Percent
1999-01-01	23.6
1999-04-01	23.3
1999-07-01	23.1
1999-10-01	22.6
2000-01-01	22.1
2000-04-01	22
2000-07-01	22
2000-10-01	21.7
2001-01-01	23.6
2001-04-01	23.6
2001-07-01	23.5
2001-10-01	23
2002-01-01	22.1
2002-04-01	21.5
2002-07-01	21.3
2002-10-01	21
2003-01-01	20.5
2003-04-01	20.2
2003-07-01	20
2003-10-01	19.5
2004-01-01	19.5
2004-04-01	19.2
2004-07-01	19.2
2004-10-01	18.5
2005-01-01	19
2005-04-01	18.7
2005-07-01	19.1
2005-10-01	18.4
2006-01-01	18
2006-04-01	17.7
2006-07-01	17.9
2006-10-01	17.2
2007-01-01	17
2007-04-01	16.9
2007-07-01	17.1
2007-10-01	16.5
2008-01-01	16.2
2008-04-01	16
2008-07-01	16.3
2008-10-01	15.4
2009-01-01	15
2009-04-01	15.2
2009-07-01	15.6
2009-10-01	14.9
2010-01-01	14.5
2010-04-01	14.2
2010-07-01	14.5
2010-10-01	14
2011-01-01	14
2011-04-01	13.7
2011-07-01	14
2011-10-01	13.5
2012-01-01	13.2
2012-04-01	13.1
2012-07-01	13.3
2012-10-01	12.8
2013-01-01	12.7
2013-04-01	12.9
2013-07-01	13.1
2013-10-01	12.7
2014-01-01	12.8
2014-04-01	12.6
2014-07-01	13
2014-10-01	12.3
2015-01-01	12.6
2015-04-01	12.2
2015-07-01	13.1
2015-10-01	12.7
2016-01-01	12.6
2016-04-01	12.4
2016-07-01	12.8
2016-10-01	12.6
2017-01-01	12.8
2017-04-01	12.9
2017-07-01	13.3
2017-10-01	12.9
2018-01-01	13.1
2018-04-01	12.9
2018-07-01	13.3