Quarter	Percent
1998-01-01	76.0
1998-04-01	75.7
1998-07-01	76.7
1998-10-01	75.8
1999-01-01	75.5
1999-04-01	75.2
1999-07-01	76
1999-10-01	75.6
2000-01-01	75.6
2000-04-01	76.7
2000-07-01	76.5
2000-10-01	76.6
2001-01-01	75.9
2001-04-01	75.8
2001-07-01	75.1
2001-10-01	74.9
2002-01-01	73.5
2002-04-01	72.9
2002-07-01	72.5
2002-10-01	72.3
2003-01-01	71.1
2003-04-01	69.6
2003-07-01	69.3
2003-10-01	70.2
2004-01-01	68.6
2004-04-01	68.5
2004-07-01	68.7
2004-10-01	68.9
2005-01-01	67.7
2005-04-01	67.3
2005-07-01	66.3
2005-10-01	66.8
2006-01-01	65.8
2006-04-01	65.6
2006-07-01	66
2006-10-01	66.6
2007-01-01	65.3
2007-04-01	64.5
2007-07-01	64.8
2007-10-01	64.6
2008-01-01	64.1
2008-04-01	63.5
2008-07-01	64.5
2008-10-01	63.5
2009-01-01	62.7
2009-04-01	62.5
2009-07-01	62.7
2009-10-01	63.4
2010-01-01	62.2
2010-04-01	62.2
2010-07-01	62.6
2010-10-01	61.2
2011-01-01	60.4
2011-04-01	60.7
2011-07-01	60.7
2011-10-01	60.6
2012-01-01	60.2
2012-04-01	58.8
2012-07-01	58
2012-10-01	56.8
2013-01-01	56.6
2013-04-01	56.3
2013-07-01	55.5
2013-10-01	54.7
2014-01-01	54.2
2014-04-01	54.3
2014-07-01	53.1
2014-10-01	53
2015-01-01	52.3
2015-04-01	51.6
2015-07-01	51.4
2015-10-01	51.7
2016-01-01	50.3
2016-04-01	49.2
2016-07-01	48.6
2016-10-01	47.0
2017-01-01	45.8
2017-04-01	46.4
2017-07-01	45.1
2017-10-01	44.5
2018-01-01	42.9
2018-04-01	42.3