Quarter	Percent
1998-04-01	36.8
1999-04-01	34.2
2000-04-01	35.4
2001-01-01	33.5
2001-04-01	33.9
2001-07-01	32.8
2001-10-01	32.3
2002-01-01	32
2002-04-01	31.7
2002-07-01	31.9
2002-10-01	31.6
2003-01-01	31.3
2003-04-01	31.3
2003-07-01	30.9
2003-10-01	30.9
2004-01-01	30.9
2004-04-01	30.4
2004-07-01	30.1
2004-10-01	29.7
2005-01-01	30.3
2005-04-01	32
2005-07-01	31.6
2005-10-01	30
2006-01-01	29.3
2006-04-01	30.5
2006-07-01	31.1
2006-10-01	30.8
2007-01-01	30.9
2007-04-01	30.5
2007-07-01	30.1
2007-10-01	30.8
2008-01-01	31.5
2008-04-01	31.2
2008-07-01	30.6
2008-10-01	30.5
2009-01-01	29.9
2009-04-01	30.1
2009-07-01	30.3
2009-10-01	29.9
2010-01-01	29.9
2010-04-01	30.2
2010-07-01	29.8
2010-10-01	29.1
2011-01-01	27.8
2011-04-01	28
2011-07-01	28.2
2011-10-01	27.6
2012-01-01	27.8
2012-04-01	26.9
2012-07-01	26.9
2012-10-01	26.3
2013-01-01	26.9
2013-04-01	26.9
2013-07-01	26.9
2013-10-01	25.9
2014-01-01	25.5
2014-04-01	24.7
2014-07-01	24.8
2014-10-01	25.4
2015-01-01	24.8
2015-04-01	24.6
2015-07-01	24.5
2015-10-01	24.0
2016-01-01	24.0
2016-04-01	23.1
2016-07-01	22.9
2016-10-01	22.6
2017-01-01	22.2
2017-04-01	21.9
2017-07-01	21.9
2017-10-01	22.7
2018-01-01	22.0
2018-04-01	21.6