Quarter	Percent
1998-01-01	38.6
1998-04-01	39.4
1998-07-01	38.3
1998-10-01	39.3
1999-01-01	39
1999-04-01	40.6
1999-07-01	38.9
1999-10-01	40.7
2000-01-01	41.4
2000-04-01	41.8
2000-07-01	43.8
2000-10-01	44.7
2001-01-01	45.1
2001-04-01	45.8
2001-07-01	47.6
2001-10-01	47.7
2002-01-01	46.6
2002-04-01	48.1
2002-07-01	49.4
2002-10-01	49.8
2003-01-01	48.7
2003-04-01	50.7
2003-07-01	53.5
2003-10-01	51.2
2004-01-01	51
2004-04-01	52
2004-07-01	51.5
2004-10-01	51.2
2005-01-01	51.3
2005-04-01	52.6
2005-07-01	53.9
2005-10-01	53.4
2006-01-01	53.3
2006-04-01	55
2006-07-01	55.2
2006-10-01	55.7
2007-01-01	54
2007-04-01	55.6
2007-07-01	55.9
2007-10-01	54.9
2008-01-01	55.7
2008-04-01	57.8
2008-07-01	57.7
2008-10-01	57.1
2009-01-01	54.8
2009-04-01	55.4
2009-07-01	55
2009-10-01	53.3
2010-01-01	54.4
2010-04-01	55.9
2010-07-01	56
2010-10-01	56.1
2011-01-01	55.3
2011-04-01	57.7
2011-07-01	56.9
2011-10-01	57.1
2012-01-01	55.4
2012-04-01	57.8
2012-07-01	56.3
2012-10-01	57
2013-01-01	55.2
2013-04-01	57.1
2013-07-01	57.6
2013-10-01	56
2014-01-01	56.2
2014-04-01	56.3
2014-07-01	57
2014-10-01	57.6
2015-01-01	56.6
2015-04-01	56.7
2015-07-01	58.0
2015-10-01	58.3
2016-01-01	57.5
2016-04-01	59.9
2016-07-01	61.6
2016-10-01	60.2
2017-01-01	59.5
2017-04-01	61.4
2017-07-01	62.2
2017-10-01	63.4
2018-01-01	63.3
2018-04-01	64.0