Quarter	Percent
1999-01-01	27.5
1999-04-01	29.3
1999-07-01	31
1999-10-01	30.9
2000-01-01	31.8
2000-04-01	33
2000-07-01	33.7
2000-10-01	34.3
2001-01-01	33.1
2001-04-01	34.2
2001-07-01	34.6
2001-10-01	34.6
2002-01-01	34.2
2002-04-01	34.9
2002-07-01	35.7
2002-10-01	37
2003-01-01	36.6
2003-04-01	38.3
2003-07-01	38.1
2003-10-01	38.2
2004-01-01	38
2004-04-01	37.8
2004-07-01	38.3
2004-10-01	39.5
2005-01-01	39.8
2005-04-01	40.2
2005-07-01	41
2005-10-01	41.2
2006-01-01	41.4
2006-04-01	41.4
2006-07-01	40.8
2006-10-01	41.2
2007-01-01	40.5
2007-04-01	40.2
2007-07-01	40.6
2007-10-01	39.1
2008-01-01	36.7
2008-04-01	37.8
2008-07-01	38.2
2008-10-01	38.2
2009-01-01	37.9
2009-04-01	38.8
2009-07-01	39.3
2009-10-01	38.8
2010-01-01	37.6
2010-04-01	38.9
2010-07-01	39.3
2010-10-01	38.6
2011-01-01	38.2
2011-04-01	39
2011-07-01	39.8
2011-10-01	40.2
2012-01-01	39
2012-04-01	41.5
2012-07-01	42.5
2012-10-01	42.5
2013-01-01	42.5
2013-04-01	44.6
2013-07-01	45.7
2013-10-01	46.5
2014-01-01	47.6
2014-04-01	48.9
2014-07-01	50.9
2014-10-01	51.1
2015-01-01	51.1
2015-04-01	54.1
2015-07-01	55.9
2015-10-01	56.4
2016-01-01	57.8
2016-04-01	59.2
2016-07-01	60.4
2016-10-01	61.2
2017-01-01	60.6
2017-04-01	62.0
2017-07-01	63.6
2017-10-01	64.1
2018-01-01	64.0
2018-04-01	63.9