Quarter	Percent
1998-01-01	37.5
1999-01-01	37.3
1999-04-01	38.5
1999-07-01	38
1999-10-01	38.4
2000-01-01	37.5
2000-04-01	38.5
2000-07-01	38
2000-10-01	38
2001-01-01	37.7
2001-04-01	37.5
2001-07-01	37.6
2001-10-01	37.1
2002-01-01	36.1
2002-04-01	36.5
2002-07-01	36.1
2002-10-01	36.3
2003-01-01	36.1
2003-04-01	35.4
2003-07-01	35.2
2003-10-01	36.1
2004-01-01	37.1
2004-04-01	36.9
2004-07-01	35.7
2004-10-01	36.3
2005-01-01	35.7
2005-04-01	35.5
2005-07-01	34.1
2005-10-01	35.1
2006-01-01	34.7
2006-04-01	34.4
2006-07-01	33.1
2006-10-01	33.9
2007-01-01	33.5
2007-04-01	33.4
2007-07-01	31.8
2007-10-01	33
2008-01-01	32.7
2008-04-01	32.7
2008-07-01	31.5
2008-10-01	31.8
2009-01-01	31.7
2009-04-01	31.5
2009-07-01	30.3
2009-10-01	31.6
2010-01-01	31.5
2010-04-01	31.5
2010-07-01	30.4
2010-10-01	31
2011-01-01	30.9
2011-04-01	31.3
2011-07-01	30.3
2011-10-01	30.5
2012-01-01	30.4
2012-04-01	30.4
2012-07-01	29.1
2012-10-01	30
2013-01-01	29.9
2013-04-01	29.6
2013-07-01	28.4
2013-10-01	29.5
2014-01-01	29.3
2014-04-01	29.2
2014-07-01	28.9
2014-10-01	29.4
2015-01-01	29.7
2015-04-01	29.5
2015-07-01	28.4
2015-10-01	28.8
2016-01-01	28.9
2016-04-01	28.6
2016-07-01	27.4
2016-10-01	28.4
2017-01-01	28.6
2017-04-01	28.4
2017-07-01	27.7
2017-10-01	28.0
2018-01-01	28.4
2018-04-01	28.5