Quarter	Percent
1999-01-01	28.4
2000-01-01	29.4
2001-01-01	30.7
2002-01-01	33.8
2003-01-01	36.3
2003-04-01	37.3
2003-07-01	37.2
2003-10-01	37.2
2004-01-01	37.5
2004-04-01	37.7
2004-07-01	38.2
2004-10-01	37.9
2005-01-01	38.6
2005-04-01	39.2
2005-07-01	38.5
2005-10-01	37.9
2006-01-01	38.2
2006-04-01	38.4
2006-07-01	38.1
2006-10-01	37.8
2007-01-01	37.9
2007-04-01	39.0
2007-07-01	38.2
2007-10-01	37.8
2008-01-01	37.6
2008-04-01	38.4
2008-07-01	38.2
2008-10-01	38.5
2009-01-01	38.5
2009-04-01	39.4
2009-07-01	39.0
2009-10-01	38.8
2010-01-01	38.9
2010-04-01	39.9
2010-07-01	40.2
2010-10-01	39.9
2011-01-01	40.0
2011-04-01	41.4
2011-07-01	41.6
2011-10-01	42.5
2012-01-01	43.1
2012-04-01	44.1
2012-07-01	45
2012-10-01	45.7
2013-01-01	45.1
2013-04-01	45.7
2013-07-01	45.9
2013-10-01	45.7
2014-01-01	46
2014-04-01	46.9
2014-07-01	47.1
2014-10-01	47.7
2015-01-01	48.0
2015-04-01	49.1
2015-07-01	49.0
2015-10-01	48.8
2016-01-01	49.3
2016-04-01	49.8
2016-07-01	50.1
2016-10-01	50.0
2017-01-01	50.4
2017-04-01	51.7
2017-07-01	51.1
2017-10-01	51.9
2018-01-01	51.8
2018-04-01	52.1