Quarter	Percent
1999-01-01	27.1
2000-01-01	28.2
2001-01-01	28.5
2002-01-01	31
2003-01-01	34.7
2003-04-01	35.7
2003-07-01	34.1
2003-10-01	34.8
2004-01-01	35.1
2004-04-01	35.8
2004-07-01	36.4
2004-10-01	36.9
2005-01-01	37.6
2005-04-01	38.3
2005-07-01	37.0
2005-10-01	36.6
2006-01-01	37.7
2006-04-01	37.9
2006-07-01	37.4
2006-10-01	37.4
2007-01-01	37.7
2007-04-01	38.5
2007-07-01	36.8
2007-10-01	37.3
2008-01-01	36.7
2008-04-01	37.4
2008-07-01	37.1
2008-10-01	37.8
2009-01-01	38.3
2009-04-01	39.2
2009-07-01	38.0
2009-10-01	38.5
2010-01-01	38.9
2010-04-01	39.6
2010-07-01	39.7
2010-10-01	39.7
2011-01-01	39.8
2011-04-01	41.4
2011-07-01	41.2
2011-10-01	42.5
2012-01-01	43.0
2012-04-01	44.1
2012-07-01	44.2
2012-10-01	45.7
2013-01-01	45.4
2013-04-01	45.7
2013-07-01	46.4
2013-10-01	46.5
2014-01-01	47.3
2014-04-01	48.7
2014-07-01	48.8
2014-10-01	49.2
2015-01-01	49.6
2015-04-01	51.0
2015-07-01	50.4
2015-10-01	50.1
2016-01-01	50.9
2016-04-01	51.3
2016-07-01	51.6
2016-10-01	51.7
2017-01-01	52.8
2017-04-01	53.4
2017-07-01	52.6
2017-10-01	53.1
2018-01-01	54.1
2018-04-01	53.7