Quarter	Percent
1998-01-01	23.2
1998-04-01	22.9
1998-07-01	22.7
1998-10-01	22.8
1999-01-01	21.9
1999-04-01	21.9
1999-07-01	22.2
1999-10-01	22.4
2000-01-01	22.1
2000-04-01	21.7
2000-07-01	21.7
2000-10-01	22
2001-01-01	21.8
2001-04-01	22.1
2001-07-01	22.2
2001-10-01	22.4
2002-01-01	22.1
2002-04-01	21.1
2002-07-01	20.9
2002-10-01	20.8
2003-01-01	20.6
2003-04-01	20.3
2003-07-01	19.9
2003-10-01	20
2004-01-01	19.2
2004-04-01	18.8
2004-07-01	18.6
2004-10-01	18.8
2005-01-01	18.8
2005-04-01	18.4
2005-07-01	18.5
2005-10-01	18.4
2006-01-01	18.4
2006-04-01	18.1
2006-07-01	17.7
2006-10-01	18
2007-01-01	18.2
2007-04-01	18.1
2007-07-01	18.1
2007-10-01	18.3
2008-01-01	18.1
2008-04-01	17.9
2008-07-01	18
2008-10-01	18.2
2009-01-01	17.7
2009-04-01	17.2
2009-07-01	17
2009-10-01	17.1
2010-01-01	16.9
2010-04-01	16.5
2010-07-01	16.7
2010-10-01	16.9
2011-01-01	17
2011-04-01	17.1
2011-07-01	16.8
2011-10-01	16.6
2012-01-01	16.5
2012-04-01	16.3
2012-07-01	16.1
2012-10-01	16.1
2013-01-01	16.4
2013-04-01	15.8
2013-07-01	15.9
2013-10-01	16.4
2014-01-01	15.9
2014-04-01	15.6
2014-07-01	15.4
2014-10-01	15.7
2015-01-01	15.4
2015-04-01	14.6
2015-07-01	14.1
2015-10-01	14.4
2016-01-01	14.5
2016-04-01	14.2
2016-07-01	14.2
2016-10-01	15.2
2017-01-01	15.3
2017-04-01	14.5
2017-07-01	14.8
2017-10-01	15.4
2018-01-01	15.5
2018-04-01	14.7