Quarter	Percent
1999-04-01	37.1
1999-07-01	37.2
1999-10-01	36.4
2000-01-01	36
2000-04-01	35.1
2000-07-01	35.4
2000-10-01	34.8
2001-01-01	34.7
2001-04-01	34
2001-07-01	33.7
2001-10-01	33.4
2002-01-01	32.9
2002-04-01	32.4
2002-07-01	33.5
2002-10-01	33.4
2003-01-01	33
2003-04-01	32.8
2003-07-01	33
2003-10-01	32.5
2004-01-01	32.4
2004-04-01	32
2004-07-01	32.2
2004-10-01	31.5
2005-01-01	30.8
2005-04-01	30.4
2005-07-01	30.3
2005-10-01	30.1
2006-01-01	29.7
2006-04-01	29.8
2006-07-01	29.5
2006-10-01	29.1
2007-01-01	27.8
2007-04-01	27.5
2007-07-01	27.5
2007-10-01	27.8
2008-01-01	27.4
2008-04-01	27.8
2008-07-01	27.6
2008-10-01	27.3
2009-01-01	27.9
2009-04-01	27.5
2009-07-01	26.8
2009-10-01	27.5
2010-01-01	27.4
2010-04-01	27.1
2010-07-01	27.6
2010-10-01	27.7
2011-01-01	28.0
2011-04-01	27.1
2011-07-01	27.1
2011-10-01	27.1
2012-01-01	27.0
2012-04-01	27.2
2012-07-01	27.1
2012-10-01	26.9
2013-01-01	26.5
2013-04-01	25.7
2013-07-01	25.9
2013-10-01	25.8
2014-01-01	25.7
2014-04-01	25.9
2014-07-01	25.6
2014-10-01	25.8
2015-01-01	26.0
2015-04-01	25.2
2015-07-01	25.8
2015-10-01	25.0
2016-01-01	25.4
2016-04-01	25.1
2016-07-01	25.1
2016-10-01	25.4
2017-01-01	24.9
2017-04-01	25.3
2017-07-01	23.4
2017-10-01	23.3
2018-01-01	23.7
2018-04-01	23.1