Quarter	Percent
1998-01-01	37.1
1998-04-01	37
1998-07-01	36.5
1998-10-01	36.7
1999-01-01	36
1999-04-01	36.3
1999-07-01	36.3
1999-10-01	36.3
2000-01-01	36.3
2000-04-01	36.1
2000-07-01	36
2000-10-01	36.3
2001-01-01	36.6
2001-04-01	36.7
2001-07-01	36.6
2001-10-01	36.9
2002-01-01	36.5
2002-04-01	35.9
2002-07-01	35.5
2002-10-01	35.5
2003-01-01	35.3
2003-04-01	35.1
2003-07-01	34.9
2003-10-01	34.9
2004-01-01	34
2004-04-01	33.7
2004-07-01	33.8
2004-10-01	33.8
2005-01-01	33.8
2005-04-01	33.6
2005-07-01	33.6
2005-10-01	33.6
2006-01-01	33.3
2006-04-01	33.4
2006-07-01	33.2
2006-10-01	33.5
2007-01-01	33.5
2007-04-01	33.5
2007-07-01	33.3
2007-10-01	33.5
2008-01-01	33.6
2008-04-01	33.3
2008-07-01	33.3
2008-10-01	33.3
2009-01-01	32.9
2009-04-01	32.6
2009-07-01	32.2
2009-10-01	32.5
2010-01-01	32.2
2010-04-01	32.1
2010-07-01	32.1
2010-10-01	32.3
2011-01-01	32.6
2011-04-01	32.8
2011-07-01	32.8
2011-10-01	32.8
2012-01-01	32.7
2012-04-01	32.6
2012-07-01	32.5
2012-10-01	32.4
2013-01-01	32.7
2013-04-01	32.3
2013-07-01	32.3
2013-10-01	32.8
2014-01-01	32.6
2014-04-01	32.5
2014-07-01	32.4
2014-10-01	32.8
2015-01-01	32.7
2015-04-01	32.3
2015-07-01	31.8
2015-10-01	31.9
2016-01-01	32.0
2016-04-01	31.7
2016-07-01	31.4
2016-10-01	32.1
2017-01-01	32.0
2017-04-01	31.4
2017-07-01	31.5
2017-10-01	32.1
2018-01-01	32.3
2018-04-01	31.5