Quarter	Percent
1999-01-01	17.7
1999-04-01	19.1
1999-07-01	20.3
1999-10-01	20.4
2000-01-01	20.8
2000-04-01	21.9
2000-07-01	22.7
2000-10-01	23.3
2001-01-01	22.6
2001-04-01	23.1
2001-07-01	24
2001-10-01	24.2
2002-01-01	24.3
2002-04-01	25
2002-07-01	25.8
2002-10-01	27.3
2003-01-01	27.5
2003-04-01	28.9
2003-07-01	29.4
2003-10-01	30
2004-01-01	30.3
2004-04-01	30.4
2004-07-01	31.2
2004-10-01	32.3
2005-01-01	32.3
2005-04-01	32.8
2005-07-01	33.4
2005-10-01	33.5
2006-01-01	33.3
2006-04-01	33.4
2006-07-01	32.9
2006-10-01	33.1
2007-01-01	32.5
2007-04-01	32.7
2007-07-01	32.3
2007-10-01	31.4
2008-01-01	30.2
2008-04-01	30.6
2008-07-01	31.4
2008-10-01	31.4
2009-01-01	31.1
2009-04-01	31.8
2009-07-01	32
2009-10-01	32.7
2010-01-01	32.3
2010-04-01	33.4
2010-07-01	34.2
2010-10-01	34.4
2011-01-01	34.6
2011-04-01	35.1
2011-07-01	35.7
2011-10-01	35.6
2012-01-01	34.8
2012-04-01	36.4
2012-07-01	37
2012-10-01	36.4
2013-01-01	36.3
2013-04-01	37.6
2013-07-01	38.4
2013-10-01	39.3
2014-01-01	40.2
2014-04-01	41.3
2014-07-01	42.6
2014-10-01	42.9
2015-01-01	43.0
2015-04-01	45.1
2015-07-01	46.4
2015-10-01	46.7
2016-01-01	47.9
2016-04-01	49.8
2016-07-01	50.6
2016-10-01	51.1
2017-01-01	50.1
2017-04-01	51.2
2017-07-01	52.4
2017-10-01	53.0
2018-01-01	53.6
2018-04-01	53.5