Quarter	Percent
1998-01-01	52.5
1998-04-01	53.7
1998-07-01	51.7
1998-10-01	51.3
1999-01-01	53.1
1999-04-01	54.1
1999-07-01	53.1
1999-10-01	53
2000-01-01	54.8
2000-04-01	56.1
2000-07-01	55.6
2000-10-01	55.9
2001-01-01	57.5
2001-04-01	58.9
2001-07-01	58.4
2001-10-01	59.1
2002-01-01	61.4
2002-04-01	61.7
2002-07-01	60.9
2002-10-01	61.1
2003-01-01	62.8
2003-04-01	64.2
2003-07-01	63.1
2003-10-01	62.8
2004-01-01	64.7
2004-04-01	65.4
2004-07-01	64.7
2004-10-01	64.5
2005-01-01	65.9
2005-04-01	67.3
2005-07-01	66.1
2005-10-01	64.7
2006-01-01	66.7
2006-04-01	67.4
2006-07-01	66
2006-10-01	65.7
2007-01-01	67.7
2007-04-01	68.7
2007-07-01	67.9
2007-10-01	67.9
2008-01-01	69.7
2008-04-01	69.7
2008-07-01	68.2
2008-10-01	67.8
2009-01-01	69.1
2009-04-01	69.1
2009-07-01	67.1
2009-10-01	67.3
2010-01-01	69.9
2010-04-01	70.3
2010-07-01	67.6
2010-10-01	68.5
2011-01-01	70.8
2011-04-01	70.7
2011-07-01	68.7
2011-10-01	70
2012-01-01	69.6
2012-04-01	69.4
2012-07-01	67.8
2012-10-01	68.1
2013-01-01	69
2013-04-01	69.2
2013-07-01	67.5
2013-10-01	68.1
2014-01-01	69
2014-04-01	68.5
2014-07-01	66.9
2014-10-01	66.7
2015-01-01	67.4
2015-04-01	68.1
2015-07-01	67.2
2015-10-01	67.3
2016-01-01	68.7
2016-04-01	68.8
2016-07-01	67.1
2016-10-01	67.5
2017-01-01	68.2
2017-04-01	69.0
2017-07-01	67.3
2017-10-01	68.9
2018-01-01	70.1
2018-04-01	70.6