Quarter	Percent
1999-04-01	63.7
2000-01-01	62.6
2000-04-01	61.4
2000-07-01	60.5
2000-10-01	59.6
2001-01-01	60
2001-04-01	60.1
2001-07-01	60.1
2001-10-01	59.1
2002-01-01	58.3
2002-04-01	57.1
2002-07-01	55.8
2002-10-01	55.7
2003-01-01	54.6
2003-04-01	54.5
2003-07-01	54.4
2003-10-01	54.5
2004-01-01	53.6
2004-04-01	53.7
2004-07-01	52.9
2004-10-01	52.3
2005-01-01	52.3
2005-04-01	51.9
2005-07-01	51.7
2005-10-01	51.7
2006-01-01	51.8
2006-04-01	50.7
2006-07-01	50
2006-10-01	49.2
2007-01-01	48.3
2007-04-01	47.2
2007-07-01	46.7
2007-10-01	46.8
2008-01-01	46.3
2008-04-01	45.5
2008-07-01	44.9
2008-10-01	44.3
2009-01-01	43.3
2009-04-01	43.6
2009-07-01	42.9
2009-10-01	42.8
2010-01-01	44.7
2010-04-01	44.3
2010-07-01	43.9
2010-10-01	43.5
2011-01-01	43.3
2011-04-01	42.6
2011-07-01	41.9
2011-10-01	40.6
2012-01-01	40.2
2012-04-01	39.2
2012-07-01	39.1
2012-10-01	38.2
2013-01-01	37.7
2013-04-01	36.8
2013-07-01	36.0
2013-10-01	35.6
2014-01-01	35.8
2014-04-01	35.3
2014-07-01	34.9
2014-10-01	34.5
2015-01-01	33.6
2015-04-01	32.7
2015-07-01	32.9
2015-10-01	32.4
2016-01-01	31.8
2016-04-01	31.6
2016-07-01	31.8
2016-10-01	31.3
2017-01-01	31.0
2017-04-01	30.2
2017-07-01	30.6
2017-10-01	30.1
2018-01-01	30.1
2018-04-01	29.3