Quarter	Percent
1998-01-01	62.6
1998-04-01	61.6
1998-07-01	60.2
1998-10-01	60.3
1999-01-01	62
1999-04-01	61.9
1999-07-01	60.9
1999-10-01	61.8
2000-01-01	62.5
2000-04-01	61.9
2000-07-01	60.8
2000-10-01	61.2
2001-01-01	63.6
2001-04-01	63.7
2001-07-01	62.9
2001-10-01	63.4
2002-01-01	64.9
2002-04-01	64.7
2002-07-01	63.7
2002-10-01	64.8
2003-01-01	65.4
2003-04-01	65.4
2003-07-01	64.5
2003-10-01	66.4
2004-01-01	63.6
2004-04-01	63.3
2004-07-01	63.5
2004-10-01	64.7
2005-01-01	65.6
2005-04-01	66
2005-07-01	66.6
2005-10-01	66.4
2006-01-01	66.5
2006-04-01	67.7
2006-07-01	68.3
2006-10-01	68.2
2007-01-01	69.9
2007-04-01	69.2
2007-07-01	68.4
2007-10-01	69.2
2008-01-01	69.4
2008-04-01	68.6
2008-07-01	68.9
2008-10-01	70.1
2009-01-01	70.8
2009-04-01	71.7
2009-07-01	71.1
2009-10-01	71.1
2010-01-01	71.2
2010-04-01	71.9
2010-07-01	73
2010-10-01	71.5
2011-01-01	72.4
2011-04-01	74.1
2011-07-01	73.6
2011-10-01	71.5
2012-01-01	71.2
2012-04-01	71.6
2012-07-01	71.6
2012-10-01	71.4
2013-01-01	72.5
2013-04-01	73.3
2013-07-01	73.1
2013-10-01	72.6
2014-01-01	73.2
2014-04-01	73.2
2014-07-01	72.4
2014-10-01	72.7
2015-01-01	74.2
2015-04-01	74.4
2015-07-01	73.7
2015-10-01	72.9
2016-01-01	74.3
2016-04-01	73.4
2016-07-01	73.3
2016-10-01	72.6
2017-01-01	74.1
2017-04-01	74.5
2017-07-01	73.2
2017-10-01	73.5
2018-01-01	73.9
2018-04-01	74.1