Quarter	Percent
1998-01-01	44.7
1998-04-01	43.3
1998-07-01	43.7
1998-10-01	44.7
1999-01-01	43.5
1999-04-01	42.1
1999-07-01	43.0
1999-10-01	42.2
2000-01-01	41.5
2000-04-01	39.9
2000-07-01	41.3
2000-10-01	41.7
2001-01-01	41.8
2001-04-01	41.6
2001-07-01	42.7
2001-10-01	42.7
2002-01-01	41.9
2002-04-01	41.8
2002-07-01	42
2002-10-01	44.1
2003-01-01	42.9
2003-04-01	41.4
2003-07-01	40.9
2003-10-01	40.4
2004-01-01	39.4
2004-04-01	38
2004-07-01	39.7
2004-10-01	38.8
2005-01-01	38.2
2005-04-01	37.2
2005-07-01	39.1
2005-10-01	37.9
2006-01-01	37.3
2006-04-01	36.7
2006-07-01	38.7
2006-10-01	37.9
2007-01-01	37.8
2007-04-01	37.1
2007-07-01	38
2007-10-01	38.5
2008-01-01	37.3
2008-04-01	37.3
2008-07-01	39.4
2008-10-01	38.3
2009-01-01	38.5
2009-04-01	36.7
2009-07-01	37.3
2009-10-01	36.4
2010-01-01	35.7
2010-04-01	34.2
2010-07-01	33.6
2010-10-01	33.3
2011-01-01	36
2011-04-01	34.6
2011-07-01	37.3
2011-10-01	35.7
2012-01-01	34.4
2012-04-01	34.3
2012-07-01	36.7
2012-10-01	34.2
2013-01-01	33.1
2013-04-01	32.5
2013-07-01	35.3
2013-10-01	34.1
2014-01-01	33.6
2014-04-01	32.5
2014-07-01	35.9
2014-10-01	33.3
2015-01-01	33.4
2015-04-01	31.1
2015-07-01	34.6
2015-10-01	32.1
2016-01-01	32.6
2016-04-01	30.1
2016-07-01	31.2
2016-10-01	31.1
2017-01-01	31.5
2017-04-01	30.9
2017-07-01	33.8
2017-10-01	33.2
2018-01-01	30.7
2018-04-01	30.4