Quarter	Percent
1998-04-01	71.9
1999-04-01	72.2
2000-04-01	71.6
2001-04-01	73.2
2002-04-01	73.9
2003-04-01	74.1
2004-04-01	73.9
2005-04-01	74.3
2006-04-01	74.7
2007-04-01	75
2008-04-01	76.6
2009-04-01	77.1
2010-01-01	75.3
2010-04-01	74.9
2010-07-01	75.6
2010-10-01	75.3
2011-01-01	76.2
2011-04-01	76.0
2011-07-01	76.1
2011-10-01	76.8
2012-01-01	76.6
2012-04-01	76.5
2012-07-01	77.1
2012-10-01	76.6
2013-01-01	77.0
2013-04-01	76.9
2013-07-01	77.1
2013-10-01	77.3
2014-01-01	77.3
2014-04-01	77.8
2014-07-01	77.9
2014-10-01	79.2
2015-01-01	78.4
2015-04-01	78.3
2015-07-01	78.5
2015-10-01	79.3
2016-01-01	80.1
2016-04-01	79.0
2016-07-01	79.1
2016-10-01	79.8
2017-01-01	79.6
2017-04-01	78.7
2017-07-01	79.4
2017-10-01	79.7
2018-01-01	79.7
2018-04-01	79.3