Quarter	Percent
1999-01-01	37.8
2000-01-01	37.5
2001-01-01	37.7
2002-01-01	37.4
2003-01-01	35.8
2003-04-01	36.0
2003-07-01	36.1
2003-10-01	36.2
2004-01-01	36.0
2004-04-01	35.9
2004-07-01	35.5
2004-10-01	35.6
2005-01-01	35.7
2005-04-01	35.5
2005-07-01	35.4
2005-10-01	35.7
2006-01-01	35.6
2006-04-01	35.9
2006-07-01	35.2
2006-10-01	35.3
2007-01-01	35.4
2007-04-01	35.2
2007-07-01	34.9
2007-10-01	34.9
2008-01-01	35.1
2008-04-01	34.9
2008-07-01	34.7
2008-10-01	34.6
2009-01-01	34.6
2009-04-01	34.1
2009-07-01	34.1
2009-10-01	34.4
2010-01-01	34.2
2010-04-01	34.2
2010-07-01	34.0
2010-10-01	34.4
2011-01-01	34.5
2011-04-01	34.4
2011-07-01	34.2
2011-10-01	34.0
2012-01-01	34.1
2012-04-01	33.7
2012-07-01	33.6
2012-10-01	33.3
2013-01-01	33.5
2013-04-01	33.2
2013-07-01	32.8
2013-10-01	32.7
2014-01-01	33.0
2014-04-01	33.0
2014-07-01	32.9
2014-10-01	32.7
2015-01-01	33.0
2015-04-01	32.8
2015-07-01	32.4
2015-10-01	32.5
2016-01-01	32.4
2016-04-01	32.6
2016-07-01	32.1
2016-10-01	32.4
2017-01-01	32.7
2017-04-01	32.3
2017-07-01	32.4
2017-10-01	32.3
2018-01-01	32.0
2018-04-01	31.9