Quarter	Percent
1999-04-01	50.2
2000-01-01	50.7
2000-04-01	49.2
2000-07-01	48.2
2000-10-01	47.3
2001-01-01	48.2
2001-04-01	48.6
2001-07-01	48.7
2001-10-01	47
2002-01-01	46.3
2002-04-01	43.8
2002-07-01	43.4
2002-10-01	43.3
2003-01-01	41.8
2003-04-01	41.8
2003-07-01	41.8
2003-10-01	41.7
2004-01-01	41
2004-04-01	41.3
2004-07-01	40.8
2004-10-01	40.3
2005-01-01	40.8
2005-04-01	40.3
2005-07-01	40.2
2005-10-01	40.7
2006-01-01	41.3
2006-04-01	39.6
2006-07-01	39.1
2006-10-01	38.3
2007-01-01	36.8
2007-04-01	36
2007-07-01	35.5
2007-10-01	35.6
2008-01-01	35.2
2008-04-01	34.5
2008-07-01	33.7
2008-10-01	33.1
2009-01-01	32.7
2009-04-01	32.5
2009-07-01	32.1
2009-10-01	32.3
2010-01-01	33.2
2010-04-01	32.4
2010-07-01	32.3
2010-10-01	32.7
2011-01-01	33.6
2011-04-01	32.8
2011-07-01	32.2
2011-10-01	31.2
2012-01-01	30.3
2012-04-01	29.3
2012-07-01	29.3
2012-10-01	28.6
2013-01-01	27.5
2013-04-01	26.2
2013-07-01	25.0
2013-10-01	24.3
2014-01-01	25.1
2014-04-01	24.6
2014-07-01	24.6
2014-10-01	23.8
2015-01-01	22.6
2015-04-01	22.2
2015-07-01	22.9
2015-10-01	21.7
2016-01-01	21.5
2016-04-01	21.8
2016-07-01	22.5
2016-10-01	21.2
2017-01-01	21.3
2017-04-01	20.8
2017-07-01	21.3
2017-10-01	20.7
2018-01-01	20.9
2018-04-01	20.2