Quarter	Percent
1998-01-01	62.7
1998-04-01	63.4
1998-07-01	62
1998-10-01	62.5
1999-01-01	63.1
1999-04-01	62.4
1999-07-01	62.6
1999-10-01	61.9
2000-01-01	63.7
2000-04-01	64.4
2000-07-01	63.9
2000-10-01	63.3
2001-01-01	66
2001-04-01	66.1
2001-07-01	65.6
2001-10-01	66.8
2002-01-01	66.2
2002-04-01	66.9
2002-07-01	66.3
2002-10-01	67.9
2003-01-01	67.8
2003-04-01	68.6
2003-07-01	69.2
2003-10-01	69.6
2004-01-01	65.7
2004-04-01	65.8
2004-07-01	67.3
2004-10-01	67.5
2005-01-01	68.9
2005-04-01	69.4
2005-07-01	69.4
2005-10-01	70.5
2006-01-01	69.9
2006-04-01	71.5
2006-07-01	71.7
2006-10-01	72.5
2007-01-01	72.6
2007-04-01	72.4
2007-07-01	72.3
2007-10-01	72.7
2008-01-01	74.3
2008-04-01	73.5
2008-07-01	74.5
2008-10-01	73.4
2009-01-01	72.5
2009-04-01	72.9
2009-07-01	72.1
2009-10-01	72.9
2010-01-01	72.8
2010-04-01	73.3
2010-07-01	72.8
2010-10-01	72.9
2011-01-01	73.5
2011-04-01	73.8
2011-07-01	73.8
2011-10-01	72.6
2012-01-01	72.9
2012-04-01	72.8
2012-07-01	72.9
2012-10-01	73.3
2013-01-01	74.4
2013-04-01	74.6
2013-07-01	75.2
2013-10-01	74.7
2014-01-01	74.5
2014-04-01	73.8
2014-07-01	73.5
2014-10-01	73.9
2015-01-01	75.3
2015-04-01	75.8
2015-07-01	75.6
2015-10-01	76.1
2016-01-01	78.2
2016-04-01	77.1
2016-07-01	76.6
2016-10-01	76.6
2017-01-01	75.7
2017-04-01	75.3
2017-07-01	76.8
2017-10-01	76.5
2018-01-01	78.1
2018-04-01	77.7