Quarter	Percent
1999-01-01	18.2
1999-04-01	19.6
1999-07-01	20.8
1999-10-01	21.1
2000-01-01	21.5
2000-04-01	22.6
2000-07-01	23.4
2000-10-01	24
2001-01-01	23.3
2001-04-01	23.8
2001-07-01	24.8
2001-10-01	24.9
2002-01-01	25.1
2002-04-01	25.7
2002-07-01	26.6
2002-10-01	28.2
2003-01-01	28.4
2003-04-01	29.7
2003-07-01	30.1
2003-10-01	30.9
2004-01-01	31.3
2004-04-01	31.3
2004-07-01	32.1
2004-10-01	33.4
2005-01-01	33.5
2005-04-01	34.2
2005-07-01	34.7
2005-10-01	34.9
2006-01-01	34.6
2006-04-01	34.8
2006-07-01	34.2
2006-10-01	34.5
2007-01-01	33.8
2007-04-01	34.2
2007-07-01	33.7
2007-10-01	33.1
2008-01-01	31.9
2008-04-01	32.2
2008-07-01	32.9
2008-10-01	33.3
2009-01-01	33.3
2009-04-01	34
2009-07-01	34.2
2009-10-01	34.9
2010-01-01	34.9
2010-04-01	36.2
2010-07-01	37.2
2010-10-01	37.5
2011-01-01	38
2011-04-01	38.7
2011-07-01	39.3
2011-10-01	39.3
2012-01-01	38.6
2012-04-01	39.9
2012-07-01	40
2012-10-01	39.4
2013-01-01	39.5
2013-04-01	41.1
2013-07-01	41.9
2013-10-01	42.5
2014-01-01	43
2014-04-01	44.3
2014-07-01	45.5
2014-10-01	45.5
2015-01-01	46.2
2015-04-01	47.9
2015-07-01	49.1
2015-10-01	49.2
2016-01-01	50.7
2016-04-01	52.0
2016-07-01	52.7
2016-10-01	53.2
2017-01-01	52.3
2017-04-01	53.3
2017-07-01	54.3
2017-10-01	54.4
2018-01-01	55.0
2018-04-01	54.8