Quarter	Percent
1999-01-01	38.9
1999-04-01	39.1
1999-07-01	39.6
1999-10-01	40.2
2000-01-01	40.5
2000-04-01	40.7
2000-07-01	41
2000-10-01	41.2
2001-01-01	39.6
2001-04-01	39.6
2001-07-01	40
2001-10-01	40.4
2002-01-01	41.5
2002-04-01	42.1
2002-07-01	42.5
2002-10-01	42.7
2003-01-01	43.2
2003-04-01	43.6
2003-07-01	44.1
2003-10-01	44.5
2004-01-01	44.7
2004-04-01	45
2004-07-01	45.3
2004-10-01	45.8
2005-01-01	46
2005-04-01	46.6
2005-07-01	46.4
2005-10-01	46.9
2006-01-01	47.4
2006-04-01	47.9
2006-07-01	47.8
2006-10-01	48.5
2007-01-01	48.6
2007-04-01	48.8
2007-07-01	49.1
2007-10-01	49.4
2008-01-01	49.7
2008-04-01	50.2
2008-07-01	50.4
2008-10-01	51.2
2009-01-01	51.4
2009-04-01	51.4
2009-07-01	51.4
2009-10-01	51.6
2010-01-01	51.9
2010-04-01	52.1
2010-07-01	52.2
2010-10-01	52.4
2011-01-01	52.5
2011-04-01	53
2011-07-01	52.8
2011-10-01	52.9
2012-01-01	53.4
2012-04-01	53.4
2012-07-01	53.5
2012-10-01	53.5
2013-01-01	53.5
2013-04-01	53.4
2013-07-01	53.2
2013-10-01	53.4
2014-01-01	53.2
2014-04-01	53.1
2014-07-01	52.8
2014-10-01	53.3
2015-01-01	53.0
2015-04-01	53.4
2015-07-01	52.8
2015-10-01	53.2
2016-01-01	53.1
2016-04-01	53.3
2016-07-01	53.0
2016-10-01	52.8
2017-01-01	52.6
2017-04-01	52.7
2017-07-01	52.5
2017-10-01	52.7
2018-01-01	52.3
2018-04-01	52.6
2018-07-01	52.3