Quarter	Percent
1998-01-01	38.6
1998-04-01	38.9
1998-07-01	38.1
1998-10-01	38.7
1999-01-01	39.2
1999-04-01	39.5
1999-07-01	39.3
1999-10-01	39.6
2000-01-01	39.1
2000-04-01	38.1
2000-07-01	38.2
2000-10-01	37.6
2001-01-01	38.3
2001-04-01	38.6
2001-07-01	39.1
2001-10-01	39.9
2002-01-01	41.4
2002-04-01	41.9
2002-07-01	43
2002-10-01	43.4
2003-01-01	43.8
2003-04-01	44.3
2003-07-01	44.8
2003-10-01	44
2004-01-01	45
2004-04-01	44.9
2004-07-01	45.2
2004-10-01	45.2
2005-01-01	46.3
2005-04-01	46.6
2005-07-01	47.7
2005-10-01	46.9
2006-01-01	48.2
2006-04-01	47.9
2006-07-01	47.8
2006-10-01	47.1
2007-01-01	47.7
2007-04-01	48.1
2007-07-01	48.6
2007-10-01	48.6
2008-01-01	49.1
2008-04-01	49.8
2008-07-01	49.3
2008-10-01	49.9
2009-01-01	50.2
2009-04-01	50.1
2009-07-01	49.6
2009-10-01	48.8
2010-01-01	49.5
2010-04-01	49.6
2010-07-01	49.6
2010-10-01	50.2
2011-01-01	50.7
2011-04-01	51.1
2011-07-01	50.6
2011-10-01	50
2012-01-01	50.5
2012-04-01	52
2012-07-01	53.2
2012-10-01	53.8
2013-01-01	54
2013-04-01	54.5
2013-07-01	55.1
2013-10-01	55.6
2014-01-01	56
2014-04-01	56.1
2014-07-01	57.5
2014-10-01	57.7
2015-01-01	57.4
2015-04-01	58.1
2015-07-01	58.2
2015-10-01	58.2
2016-01-01	59.4
2016-04-01	60.5
2016-07-01	61.1
2016-10-01	62.4
2017-01-01	62.8
2017-04-01	63.2
2017-07-01	63.9
2017-10-01	64.7
2018-01-01	65.8
2018-04-01	66.4