Quarter	Percent
1998-01-01	24.9
1998-04-01	24.7
1998-07-01	25.4
1998-10-01	24.7
1999-01-01	24.7
1999-04-01	24.2
1999-07-01	24.3
1999-10-01	23.9
2000-01-01	23
2000-04-01	22.9
2000-07-01	22.1
2000-10-01	22.4
2001-01-01	21.3
2001-04-01	21.9
2001-07-01	22.2
2001-10-01	22.0
2002-01-01	22.4
2002-04-01	21.7
2002-07-01	21.2
2002-10-01	21.4
2003-01-01	20.7
2003-04-01	20.1
2003-07-01	20.5
2003-10-01	20.2
2004-01-01	20
2004-04-01	19.5
2004-07-01	19.5
2004-10-01	18.8
2005-01-01	18.7
2005-04-01	18.5
2005-07-01	18.3
2005-10-01	17.8
2006-01-01	17.6
2006-04-01	17.3
2006-07-01	17.3
2006-10-01	17.3
2007-01-01	17.3
2007-04-01	17.3
2007-07-01	17.2
2007-10-01	17.2
2008-01-01	17.3
2008-04-01	16.7
2008-07-01	17.2
2008-10-01	17.3
2009-01-01	16.9
2009-04-01	16.8
2009-07-01	16.9
2009-10-01	16.3
2010-01-01	15.4
2010-04-01	15
2010-07-01	14.9
2010-10-01	15.3
2011-01-01	15.4
2011-04-01	14.6
2011-07-01	16.2
2011-10-01	15.8
2012-01-01	14.9
2012-04-01	14.7
2012-07-01	15.2
2012-10-01	15
2013-01-01	14.8
2013-04-01	14.7
2013-07-01	14.7
2013-10-01	13.7
2014-01-01	14.2
2014-04-01	13.8
2014-07-01	14.4
2014-10-01	14.2
2015-01-01	14.0
2015-04-01	13.6
2015-07-01	14.4
2015-10-01	13.8
2016-01-01	13.5
2016-04-01	13.9
2016-07-01	13.1
2016-10-01	13.2
2017-01-01	13.1
2017-04-01	13.1
2017-07-01	12.9
2017-10-01	12.8
2018-01-01	12.8
2018-04-01	12.4