Quarter	Percent
1998-01-01	46.3
1998-04-01	47.5
1998-07-01	46.3
1998-10-01	45.8
1999-01-01	47.9
1999-04-01	49
1999-07-01	48.9
1999-10-01	48.6
2000-01-01	50.4
2000-04-01	52.3
2000-07-01	51.5
2000-10-01	52.4
2001-01-01	54.4
2001-04-01	55.4
2001-07-01	54.3
2001-10-01	55.3
2002-01-01	57.6
2002-04-01	57.7
2002-07-01	57.6
2002-10-01	58.2
2003-01-01	59.9
2003-04-01	61.2
2003-07-01	60.6
2003-10-01	59.9
2004-01-01	61.5
2004-04-01	62.2
2004-07-01	60.9
2004-10-01	60.4
2005-01-01	60.5
2005-04-01	62.4
2005-07-01	61.3
2005-10-01	60.4
2006-01-01	62.2
2006-04-01	63.4
2006-07-01	62.2
2006-10-01	61.3
2007-01-01	63
2007-04-01	64.2
2007-07-01	63.2
2007-10-01	62.7
2008-01-01	64.8
2008-04-01	65.1
2008-07-01	63.6
2008-10-01	62.9
2009-01-01	64.1
2009-04-01	63.7
2009-07-01	61.6
2009-10-01	61.6
2010-01-01	64.2
2010-04-01	65
2010-07-01	62.6
2010-10-01	63.4
2011-01-01	65.8
2011-04-01	65.4
2011-07-01	63
2011-10-01	63.9
2012-01-01	64.3
2012-04-01	64
2012-07-01	62.6
2012-10-01	63.3
2013-01-01	64
2013-04-01	64.4
2013-07-01	61.9
2013-10-01	62.6
2014-01-01	62.8
2014-04-01	62.1
2014-07-01	61.1
2014-10-01	61.7
2015-01-01	62.5
2015-04-01	63.3
2015-07-01	62.9
2015-10-01	61.8
2016-01-01	62.8
2016-04-01	63.0
2016-07-01	61.8
2016-10-01	62.6
2017-01-01	63.4
2017-04-01	63.8
2017-07-01	62.5
2017-10-01	64.5
2018-01-01	65.6
2018-04-01	67.0