Quarter	Percent
1998-01-01	84.4
1998-04-01	84.5
1998-07-01	84.2
1998-10-01	84.2
1999-01-01	84.3
1999-04-01	84.1
1999-07-01	84
1999-10-01	84.3
2000-01-01	84.6
2000-04-01	84.1
2000-07-01	83.8
2000-10-01	83.3
2001-01-01	83.3
2001-04-01	84
2001-07-01	82.8
2001-10-01	82.2
2002-01-01	82.7
2002-04-01	82.3
2002-07-01	81.3
2002-10-01	81.2
2003-01-01	82
2003-04-01	81
2003-07-01	80
2003-10-01	79.9
2004-01-01	80.8
2004-04-01	80.2
2004-07-01	78.7
2004-10-01	78.1
2005-01-01	78.9
2005-04-01	78.7
2005-07-01	78.7
2005-10-01	77.7
2006-01-01	78.2
2006-04-01	77.3
2006-07-01	77.3
2006-10-01	77.3
2007-01-01	77
2007-04-01	76.1
2007-07-01	76.4
2007-10-01	76.7
2008-01-01	76.6
2008-04-01	74.6
2008-07-01	75
2008-10-01	75.4
2009-01-01	74.5
2009-04-01	73.1
2009-07-01	74.2
2009-10-01	74.3
2010-01-01	73.4
2010-04-01	73.1
2010-07-01	73.1
2010-10-01	72.8
2011-01-01	71.8
2011-04-01	71.7
2011-07-01	71.1
2011-10-01	70.1
2012-01-01	68.9
2012-04-01	67.8
2012-07-01	67.6
2012-10-01	67
2013-01-01	67
2013-04-01	65.9
2013-07-01	64.6
2013-10-01	63.9
2014-01-01	63
2014-04-01	62.3
2014-07-01	61.2
2014-10-01	60.4
2015-01-01	60.7
2015-04-01	60.1
2015-07-01	60.7
2015-10-01	60.1
2016-01-01	59.3
2016-04-01	57.9
2016-07-01	58.4
2016-10-01	57.5
2017-01-01	56.5
2017-04-01	55.5
2017-07-01	55.6
2017-10-01	54.3
2018-01-01	54.1
2018-04-01	53.2