Quarter	Percent
1999-01-01	58.2
1999-04-01	58.8
1999-07-01	59.8
1999-10-01	58.9
2000-01-01	59.2
2000-04-01	59
2000-07-01	59.4
2000-10-01	58.6
2001-01-01	58.5
2001-04-01	57.1
2001-07-01	56.8
2001-10-01	55
2002-01-01	54
2002-04-01	54.4
2002-07-01	53.9
2002-10-01	52.6
2003-01-01	53.5
2003-04-01	52.4
2003-07-01	50.8
2003-10-01	50.9
2004-01-01	49.5
2004-04-01	48.9
2004-07-01	47.2
2004-10-01	46.8
2005-01-01	46
2005-04-01	45.8
2005-07-01	44.1
2005-10-01	43.8
2006-01-01	44
2006-04-01	45.5
2006-07-01	44.6
2006-10-01	45
2007-01-01	44.5
2007-04-01	44
2007-07-01	41.4
2007-10-01	42.3
2008-01-01	41.5
2008-04-01	40.6
2008-07-01	39
2008-10-01	39.5
2009-01-01	41.3
2009-04-01	41.9
2009-07-01	41
2009-10-01	41.1
2010-01-01	40.2
2010-04-01	39.5
2010-07-01	40.4
2010-10-01	41
2011-01-01	41.7
2011-04-01	41.1
2011-07-01	40.9
2011-10-01	41.2
2012-01-01	41.1
2012-04-01	39.5
2012-07-01	40
2012-10-01	38.4
2013-01-01	40.1
2013-04-01	39.7
2013-07-01	40.2
2013-10-01	41.8
2014-01-01	41.6
2014-04-01	41.1
2014-07-01	40.8
2014-10-01	41.1
2015-01-01	41.8
2015-04-01	42.2
2015-07-01	41.6
2015-10-01	40.9
2016-01-01	40.7
2016-04-01	38.4
2016-07-01	40.5
2016-10-01	39.9
2017-01-01	40.6
2017-04-01	40.1
2017-07-01	39.8
2017-10-01	39.5
2018-01-01	39.0
2018-04-01	39.6