Quarter	Percent
1998-04-01	75.5
1999-04-01	75.1
2000-04-01	75.6
2001-04-01	76.8
2002-04-01	78
2003-04-01	77.3
2004-04-01	77.1
2005-04-01	77.5
2006-04-01	77.6
2007-04-01	78.5
2008-04-01	80.6
2009-04-01	80.4
2010-01-01	77.6
2010-04-01	77.9
2010-07-01	77.8
2010-10-01	78.4
2011-01-01	78.9
2011-04-01	79.4
2011-07-01	78.3
2011-10-01	79.9
2012-01-01	79.7
2012-04-01	79.8
2012-07-01	79.9
2012-10-01	80.1
2013-01-01	79.3
2013-04-01	79.7
2013-07-01	79.7
2013-10-01	80.0
2014-01-01	79.8
2014-04-01	80.6
2014-07-01	80.7
2014-10-01	81.6
2015-01-01	81.2
2015-04-01	81.0
2015-07-01	80.3
2015-10-01	81.1
2016-01-01	81.8
2016-04-01	80.9
2016-07-01	80.7
2016-10-01	81.7
2017-01-01	81.4
2017-04-01	81.0
2017-07-01	80.9
2017-10-01	81.5
2018-01-01	81.4
2018-04-01	81.1