Quarter	Percent
1998-01-01	58.9
1998-04-01	59.7
1998-07-01	58.7
1998-10-01	59.3
1999-01-01	60.5
1999-04-01	60.3
1999-07-01	60.3
1999-10-01	59.7
2000-01-01	61
2000-04-01	61.3
2000-07-01	61
2000-10-01	60.7
2001-01-01	64
2001-04-01	63.6
2001-07-01	62.9
2001-10-01	63.8
2002-01-01	63.5
2002-04-01	63.8
2002-07-01	63.7
2002-10-01	64.9
2003-01-01	64.4
2003-04-01	65.1
2003-07-01	66.1
2003-10-01	66.9
2004-01-01	62.1
2004-04-01	62.7
2004-07-01	64.3
2004-10-01	64.5
2005-01-01	65.3
2005-04-01	66.2
2005-07-01	66.6
2005-10-01	67.1
2006-01-01	66.3
2006-04-01	67.7
2006-07-01	68.3
2006-10-01	69
2007-01-01	68.7
2007-04-01	69.1
2007-07-01	68.8
2007-10-01	69.5
2008-01-01	70.4
2008-04-01	69.8
2008-07-01	69.9
2008-10-01	69.7
2009-01-01	69.1
2009-04-01	69.7
2009-07-01	68.8
2009-10-01	69.8
2010-01-01	69.9
2010-04-01	70.1
2010-07-01	69.8
2010-10-01	70.2
2011-01-01	71
2011-04-01	71.3
2011-07-01	70.8
2011-10-01	70.5
2012-01-01	70.7
2012-04-01	70.9
2012-07-01	70.9
2012-10-01	71
2013-01-01	71.3
2013-04-01	71.7
2013-07-01	71.6
2013-10-01	71.8
2014-01-01	72.4
2014-04-01	72
2014-07-01	71.4
2014-10-01	72.1
2015-01-01	73.1
2015-04-01	74.0
2015-07-01	74.1
2015-10-01	74.9
2016-01-01	76.1
2016-04-01	75.4
2016-07-01	74.7
2016-10-01	75.2
2017-01-01	74.7
2017-04-01	74.4
2017-07-01	74.9
2017-10-01	75.8
2018-01-01	76.4
2018-04-01	76.3