Quarter	Percent
1998-01-01	66.9
1998-04-01	67.5
1998-07-01	67.2
1998-10-01	67.2
1999-01-01	67.0
1999-04-01	67.0
1999-07-01	67.2
1999-10-01	67.4
2000-01-01	67.4
2000-04-01	67.6
2000-07-01	68.1
2000-10-01	68.2
2001-01-01	68.2
2001-04-01	68.2
2001-07-01	68.2
2001-10-01	68.1
2002-01-01	68.1
2002-04-01	68.1
2002-07-01	67.9
2002-10-01	66.8
2003-01-01	66.2
2003-04-01	66.4
2003-07-01	66.4
2003-10-01	66.1
2004-01-01	65.8
2004-04-01	65.6
2004-07-01	65.3
2004-10-01	64.9
2005-01-01	64.5
2005-04-01	64.7
2005-07-01	64.5
2005-10-01	64.4
2006-01-01	64.7
2006-04-01	65
2006-07-01	65
2006-10-01	64.3
2007-01-01	64.4
2007-04-01	64.5
2007-07-01	64.8
2007-10-01	64.7
2008-01-01	64.7
2008-04-01	64.8
2008-07-01	64.3
2008-10-01	64
2009-01-01	62.6
2009-04-01	62.2
2009-07-01	61.2
2009-10-01	61
2010-01-01	61
2010-04-01	60.6
2010-07-01	60.7
2010-10-01	60.4
2011-01-01	59.3
2011-04-01	59.3
2011-07-01	59.3
2011-10-01	57.4
2012-01-01	56.5
2012-04-01	56.6
2012-07-01	56.1
2012-10-01	54.7
2013-01-01	53.6
2013-04-01	54.5
2013-07-01	55.3
2013-10-01	55.3
2014-01-01	54.6
2014-04-01	56.1
2014-07-01	56.9
2014-10-01	55.7
2015-01-01	55.5
2015-04-01	56.3
2015-07-01	56.7
2015-10-01	56.8
2016-01-01	55.6
2016-04-01	57.1
2016-07-01	58.0
2016-10-01	57.5
2017-01-01	57.8
2017-04-01	59.1
2017-07-01	59.8
2017-10-01	59.7
2018-01-01	59.5
2018-04-01	60.1