Quarter	Percent
1998-01-01	42.5
1998-04-01	43.7
1998-07-01	45
1998-10-01	43.9
1999-01-01	42.6
1999-04-01	42.4
1999-07-01	43.9
1999-10-01	42.1
2000-01-01	41.8
2000-04-01	42.2
2000-07-01	43.3
2000-10-01	42.8
2001-01-01	40.2
2001-04-01	40.1
2001-07-01	41.7
2001-10-01	40.5
2002-01-01	39.2
2002-04-01	39.6
2002-07-01	41.4
2002-10-01	39.5
2003-01-01	39.3
2003-04-01	39.1
2003-07-01	40
2003-10-01	38.6
2004-01-01	41.1
2004-04-01	41.4
2004-07-01	40.5
2004-10-01	39.4
2005-01-01	39.8
2005-04-01	39.7
2005-07-01	38.2
2005-10-01	37.6
2006-01-01	38.4
2006-04-01	38.3
2006-07-01	37.3
2006-10-01	36.5
2007-01-01	35.2
2007-04-01	36.4
2007-07-01	37
2007-10-01	35.4
2008-01-01	35
2008-04-01	37.1
2008-07-01	36.4
2008-10-01	34.4
2009-01-01	33.8
2009-04-01	32.8
2009-07-01	34.7
2009-10-01	33.8
2010-01-01	34.2
2010-04-01	32.9
2010-07-01	31.3
2010-10-01	32.8
2011-01-01	32.3
2011-04-01	29.7
2011-07-01	30.5
2011-10-01	32.3
2012-01-01	33.3
2012-04-01	33.2
2012-07-01	32.7
2012-10-01	32.3
2013-01-01	31.1
2013-04-01	30.6
2013-07-01	30.5
2013-10-01	30.6
2014-01-01	30.6
2014-04-01	30.5
2014-07-01	31.8
2014-10-01	31.1
2015-01-01	29.5
2015-04-01	29.5
2015-07-01	31.2
2015-10-01	31.7
2016-01-01	29.1
2016-04-01	30.0
2016-07-01	30.3
2016-10-01	31.4
2017-01-01	29.4
2017-04-01	28.8
2017-07-01	31.0
2017-10-01	30.7
2018-01-01	29.7
2018-04-01	29.9