Quarter	Percent
1998-01-01	38.0
1998-04-01	38.7
1998-07-01	37.9
1998-10-01	38.6
1999-01-01	38.1
1999-04-01	37.5
1999-07-01	38.1
1999-10-01	37.7
2000-01-01	36.2
2000-04-01	35.2
2000-07-01	36.6
2000-10-01	37.0
2001-01-01	36.2
2001-04-01	36.6
2001-07-01	38.2
2001-10-01	37.4
2002-01-01	36.7
2002-04-01	36.7
2002-07-01	36.2
2002-10-01	36.4
2003-01-01	35.3
2003-04-01	34.5
2003-07-01	34.1
2003-10-01	33.5
2004-01-01	32.5
2004-04-01	32
2004-07-01	32.2
2004-10-01	31.6
2005-01-01	30.6
2005-04-01	30.6
2005-07-01	31.1
2005-10-01	30.8
2006-01-01	30.6
2006-04-01	30.9
2006-07-01	31.2
2006-10-01	29.9
2007-01-01	30
2007-04-01	30
2007-07-01	30.4
2007-10-01	30.2
2008-01-01	29.6
2008-04-01	30.8
2008-07-01	31.1
2008-10-01	29.9
2009-01-01	30.1
2009-04-01	29.9
2009-07-01	28.9
2009-10-01	27.7
2010-01-01	27.2
2010-04-01	27.3
2010-07-01	24.9
2010-10-01	24.5
2011-01-01	25.3
2011-04-01	25.1
2011-07-01	25.1
2011-10-01	22.5
2012-01-01	21.8
2012-04-01	21.8
2012-07-01	21.7
2012-10-01	19.5
2013-01-01	18.1
2013-04-01	19.5
2013-07-01	22.8
2013-10-01	21.1
2014-01-01	20.9
2014-04-01	21.3
2014-07-01	23.5
2014-10-01	21.8
2015-01-01	20.4
2015-04-01	21.3
2015-07-01	23.0
2015-10-01	21.3
2016-01-01	22.1
2016-04-01	21.7
2016-07-01	22.7
2016-10-01	22.5
2017-01-01	23.2
2017-04-01	23.9
2017-07-01	24.6
2017-10-01	24.6
2018-01-01	24.6
2018-04-01	23.8