Quarter	Percent
1999-04-01	45.7
2000-04-01	47.5
2001-04-01	48
2002-04-01	47.4
2003-04-01	45.5
2004-04-01	42.8
2005-01-01	40
2005-04-01	39.1
2005-07-01	38.2
2005-10-01	37.7
2006-01-01	37.8
2006-04-01	36.6
2006-07-01	35.9
2006-10-01	35
2007-01-01	35.3
2007-04-01	33.8
2007-07-01	34.1
2007-10-01	33.6
2008-01-01	33.9
2008-04-01	32.3
2008-07-01	32.8
2008-10-01	32.2
2009-01-01	31.8
2009-04-01	30.4
2009-07-01	31.2
2009-10-01	29.6
2010-01-01	28.9
2010-04-01	29.1
2010-07-01	29.8
2010-10-01	28.9
2011-01-01	28.9
2011-04-01	27.9
2011-07-01	28.5
2011-10-01	27.5
2012-01-01	27.7
2012-04-01	27.5
2012-07-01	26.4
2012-10-01	26.1
2013-01-01	26.6
2013-04-01	25.9
2013-07-01	25.2
2013-10-01	24.4
2014-01-01	24.4
2014-04-01	25
2014-07-01	24.5
2014-10-01	24.1
2015-01-01	25.2
2015-04-01	25.5
2015-07-01	24.4
2015-10-01	23.9
2016-01-01	23.7
2016-04-01	23.4
2016-07-01	23.1
2016-10-01	22.3
2017-01-01	23.7
2017-04-01	22.1
2017-07-01	21.6
2017-10-01	21.1
2018-01-01	22.1
2018-04-01	21.9