Quarter	Percent
1999-01-01	56.7
2000-01-01	57.6
2001-01-01	58.3
2002-01-01	58
2003-01-01	58.3
2003-04-01	58.5
2003-07-01	58.9
2003-10-01	58
2004-01-01	57.9
2004-04-01	58.1
2004-07-01	58.5
2004-10-01	57.6
2005-01-01	57.3
2005-04-01	57.8
2005-07-01	58.2
2005-10-01	57.4
2006-01-01	56.9
2006-04-01	57.5
2006-07-01	58.2
2006-10-01	57.1
2007-01-01	57.0
2007-04-01	57.7
2007-07-01	58.2
2007-10-01	57.7
2008-01-01	57.6
2008-04-01	58.1
2008-07-01	58.4
2008-10-01	57.8
2009-01-01	56.9
2009-04-01	57.0
2009-07-01	57.0
2009-10-01	56.3
2010-01-01	56.2
2010-04-01	56.7
2010-07-01	57.1
2010-10-01	56.6
2011-01-01	56.2
2011-04-01	56.6
2011-07-01	56.8
2011-10-01	56.0
2012-01-01	55.6
2012-04-01	56.2
2012-07-01	56.5
2012-10-01	55.8
2013-01-01	55.0
2013-04-01	55.6
2013-07-01	55.9
2013-10-01	55.0
2014-01-01	54.3
2014-04-01	54.7
2014-07-01	54.9
2014-10-01	54.3
2015-01-01	54.0
2015-04-01	54.5
2015-07-01	54.6
2015-10-01	54.2
2016-01-01	53.9
2016-04-01	54.6
2016-07-01	54.8
2016-10-01	54.3
2017-01-01	54.0
2017-04-01	55.0
2017-07-01	55.2
2017-10-01	55.0
2018-01-01	54.6
2018-04-01	55.0