Quarter	Percent
1998-01-01	51.5
1998-04-01	52.9
1998-07-01	52.9
1998-10-01	51.8
1999-01-01	53.1
1999-04-01	53.7
1999-07-01	53.0
1999-10-01	52.3
2000-01-01	53.2
2000-04-01	55.2
2000-07-01	53.3
2000-10-01	53
2001-01-01	53.2
2001-04-01	53.5
2001-07-01	51.8
2001-10-01	52.2
2002-01-01	52.7
2002-04-01	52.9
2002-07-01	52.1
2002-10-01	51.5
2003-01-01	53.3
2003-04-01	55.1
2003-07-01	55
2003-10-01	55.8
2004-01-01	56.7
2004-04-01	57.4
2004-07-01	56
2004-10-01	57.2
2005-01-01	57.9
2005-04-01	58.2
2005-07-01	57.3
2005-10-01	58.2
2006-01-01	58.6
2006-04-01	58.6
2006-07-01	57.7
2006-10-01	58.5
2007-01-01	58.5
2007-04-01	59.6
2007-07-01	58.1
2007-10-01	58.5
2008-01-01	58.9
2008-04-01	59.5
2008-07-01	58.8
2008-10-01	59.3
2009-01-01	60.2
2009-04-01	61.5
2009-07-01	61.4
2009-10-01	62
2010-01-01	62.9
2010-04-01	64.1
2010-07-01	64.1
2010-10-01	64.4
2011-01-01	62
2011-04-01	63.4
2011-07-01	60.2
2011-10-01	61.7
2012-01-01	63.3
2012-04-01	63.6
2012-07-01	60.9
2012-10-01	63.9
2013-01-01	65.2
2013-04-01	66.1
2013-07-01	63.3
2013-10-01	65.3
2014-01-01	65.8
2014-04-01	67.1
2014-07-01	63.6
2014-10-01	66.4
2015-01-01	66.6
2015-04-01	68.2
2015-07-01	65.1
2015-10-01	66.1
2016-01-01	66.8
2016-04-01	67.7
2016-07-01	66.3
2016-10-01	66.5
2017-01-01	66.6
2017-04-01	67.4
2017-07-01	64.8
2017-10-01	65.2
2018-01-01	66.7
2018-04-01	67.3