Quarter	Percent
1998-01-01	59.5
1998-04-01	60
1998-07-01	60.4
1998-10-01	60.3
1999-01-01	61.8
1999-04-01	61.8
1999-07-01	61.3
1999-10-01	61.1
2000-01-01	61.6
2000-04-01	62.2
2000-07-01	62.4
2000-10-01	61.9
2001-01-01	62.4
2001-04-01	61.8
2001-07-01	61.6
2001-10-01	61.2
2002-01-01	62.2
2002-04-01	63.6
2002-07-01	64.1
2002-10-01	64.4
2003-01-01	64.6
2003-04-01	65.3
2003-07-01	65.8
2003-10-01	65.9
2004-01-01	67.2
2004-04-01	67.6
2004-07-01	68.1
2004-10-01	67.9
2005-01-01	67.9
2005-04-01	68.5
2005-07-01	68.5
2005-10-01	68.7
2006-01-01	68.6
2006-04-01	69.2
2006-07-01	69.8
2006-10-01	69.3
2007-01-01	69.1
2007-04-01	69.5
2007-07-01	69.3
2007-10-01	68.8
2008-01-01	69.1
2008-04-01	69.5
2008-07-01	69.8
2008-10-01	69.8
2009-01-01	70.5
2009-04-01	71.2
2009-07-01	71.4
2009-10-01	71.5
2010-01-01	71.8
2010-04-01	72.6
2010-07-01	72.6
2010-10-01	72.4
2011-01-01	72.6
2011-04-01	72.2
2011-07-01	72.8
2011-10-01	73.6
2012-01-01	73.7
2012-04-01	73.9
2012-07-01	74.1
2012-10-01	74.2
2013-01-01	73.8
2013-04-01	74.7
2013-07-01	74.7
2013-10-01	74
2014-01-01	74.8
2014-04-01	75.5
2014-07-01	76
2014-10-01	76.1
2015-01-01	76.7
2015-04-01	77.9
2015-07-01	78.2
2015-10-01	77.9
2016-01-01	78.0
2016-04-01	78.1
2016-07-01	78.1
2016-10-01	76.8
2017-01-01	76.6
2017-04-01	77.9
2017-07-01	77.2
2017-10-01	76.3
2018-01-01	76.0
2018-04-01	77.2