Quarter	Percent
1998-01-01	23.1
1998-04-01	23.2
1998-07-01	22.3
1998-10-01	22.9
1999-01-01	23.2
1999-04-01	23.6
1999-07-01	22.7
1999-10-01	23.3
2000-01-01	23.1
2000-04-01	22.1
2000-07-01	22.2
2000-10-01	22.1
2001-01-01	22.7
2001-04-01	23
2001-07-01	23.4
2001-10-01	23.5
2002-01-01	25.2
2002-04-01	25.9
2002-07-01	26.2
2002-10-01	26.3
2003-01-01	27.5
2003-04-01	28.7
2003-07-01	29.2
2003-10-01	28.3
2004-01-01	29.6
2004-04-01	29.6
2004-07-01	29.4
2004-10-01	29
2005-01-01	30.4
2005-04-01	30.6
2005-07-01	31.4
2005-10-01	31
2006-01-01	31.8
2006-04-01	32.4
2006-07-01	32.3
2006-10-01	31.9
2007-01-01	32.9
2007-04-01	33.9
2007-07-01	33.5
2007-10-01	33.7
2008-01-01	34.2
2008-04-01	34.9
2008-07-01	33.9
2008-10-01	34.7
2009-01-01	35.5
2009-04-01	35.3
2009-07-01	34.8
2009-10-01	34.5
2010-01-01	35.2
2010-04-01	35.2
2010-07-01	34.9
2010-10-01	36.6
2011-01-01	36.9
2011-04-01	37.3
2011-07-01	37.2
2011-10-01	37.2
2012-01-01	37.6
2012-04-01	39
2012-07-01	39.6
2012-10-01	40
2013-01-01	40.3
2013-04-01	41.1
2013-07-01	41.8
2013-10-01	42.5
2014-01-01	43
2014-04-01	43.3
2014-07-01	44.4
2014-10-01	44.6
2015-01-01	44.8
2015-04-01	46.1
2015-07-01	46.4
2015-10-01	46.4
2016-01-01	47.3
2016-04-01	48.9
2016-07-01	49.7
2016-10-01	51.3
2017-01-01	52.2
2017-04-01	52.0
2017-07-01	53.5
2017-10-01	54.2
2018-01-01	55.7
2018-04-01	56.5