Quarter	Percent
1999-01-01	40.1
1999-04-01	39.5
1999-07-01	39.4
1999-10-01	38.3
2000-01-01	37.5
2000-04-01	37.3
2000-07-01	37.2
2000-10-01	36.6
2001-01-01	38.9
2001-04-01	39.1
2001-07-01	38.9
2001-10-01	38
2002-01-01	36.1
2002-04-01	35.3
2002-07-01	35
2002-10-01	34.4
2003-01-01	33.5
2003-04-01	33.1
2003-07-01	32.8
2003-10-01	31.8
2004-01-01	31.6
2004-04-01	31.2
2004-07-01	31.1
2004-10-01	29.8
2005-01-01	30.5
2005-04-01	30.1
2005-07-01	30.8
2005-10-01	29.4
2006-01-01	28.9
2006-04-01	28.3
2006-07-01	28.6
2006-10-01	27.2
2007-01-01	26.9
2007-04-01	26.9
2007-07-01	27.1
2007-10-01	25.9
2008-01-01	25.4
2008-04-01	25
2008-07-01	25.2
2008-10-01	23.4
2009-01-01	22.9
2009-04-01	22.9
2009-07-01	23.3
2009-10-01	22.2
2010-01-01	21.6
2010-04-01	21.2
2010-07-01	21.6
2010-10-01	20.6
2011-01-01	20.4
2011-04-01	20
2011-07-01	20.8
2011-10-01	19.9
2012-01-01	18.9
2012-04-01	19.2
2012-07-01	19.3
2012-10-01	18.3
2013-01-01	18.1
2013-04-01	18.1
2013-07-01	18.7
2013-10-01	17.9
2014-01-01	17.9
2014-04-01	17.8
2014-07-01	18.7
2014-10-01	17.6
2015-01-01	17.9
2015-04-01	17.4
2015-07-01	18.9
2015-10-01	17.7
2016-01-01	17.7
2016-04-01	17.3
2016-07-01	18.1
2016-10-01	17.6
2017-01-01	17.7
2017-04-01	18.0
2017-07-01	18.5
2017-10-01	17.8
2018-01-01	18.1
2018-04-01	17.8
2018-07-01	18.7