Quarter	Percent
1999-01-01	51.6
1999-04-01	49.4
1999-07-01	51.5
1999-10-01	51
2000-01-01	49.7
2000-04-01	47.8
2000-07-01	50.3
2000-10-01	50.1
2001-01-01	49.2
2001-04-01	49.6
2001-07-01	51
2001-10-01	49.4
2002-01-01	48
2002-04-01	46.5
2002-07-01	47.6
2002-10-01	47.8
2003-01-01	45.9
2003-04-01	44.3
2003-07-01	45.3
2003-10-01	44.1
2004-01-01	43.3
2004-04-01	42.7
2004-07-01	43.1
2004-10-01	42.4
2005-01-01	40.8
2005-04-01	40.1
2005-07-01	40.5
2005-10-01	41.6
2006-01-01	40.2
2006-04-01	39.6
2006-07-01	40.1
2006-10-01	38.8
2007-01-01	37.6
2007-04-01	37.7
2007-07-01	39.5
2007-10-01	40.6
2008-01-01	38.8
2008-04-01	37.3
2008-07-01	37.9
2008-10-01	37.3
2009-01-01	36.2
2009-04-01	35.8
2009-07-01	38.2
2009-10-01	38.4
2010-01-01	35.6
2010-04-01	35.4
2010-07-01	37.1
2010-10-01	37.5
2011-01-01	36.6
2011-04-01	38
2011-07-01	36.8
2011-10-01	37.3
2012-01-01	37.1
2012-04-01	35.7
2012-07-01	37.8
2012-10-01	37.7
2013-01-01	38.3
2013-04-01	37.3
2013-07-01	37.6
2013-10-01	37
2014-01-01	38
2014-04-01	37.3
2014-07-01	38.1
2014-10-01	38.8
2015-01-01	38.8
2015-04-01	36.6
2015-07-01	38.9
2015-10-01	38.8
2016-01-01	38.8
2016-04-01	37.9
2016-07-01	41.0
2016-10-01	41.3
2017-01-01	40.6
2017-04-01	39.1
2017-07-01	39.2
2017-10-01	39.4
2018-01-01	39.2
2018-04-01	39.4