Quarter	Percent
1999-01-01	38.6
1999-04-01	38.6
1999-07-01	38.7
1999-10-01	39.1
2000-01-01	37
2000-04-01	37
2000-07-01	37.7
2000-10-01	37.5
2001-01-01	35.8
2001-04-01	34.4
2001-07-01	34.3
2001-10-01	33.1
2002-01-01	31.5
2002-04-01	31.7
2002-07-01	31.3
2002-10-01	30.3
2003-01-01	29.8
2003-04-01	29.9
2003-07-01	30.5
2003-10-01	29.1
2004-01-01	27.1
2004-04-01	26.3
2004-07-01	26.1
2004-10-01	25.7
2005-01-01	24.5
2005-04-01	23.8
2005-07-01	24.6
2005-10-01	24.6
2006-01-01	23.4
2006-04-01	24.4
2006-07-01	25
2006-10-01	25.5
2007-01-01	24.3
2007-04-01	24.7
2007-07-01	24.8
2007-10-01	23.7
2008-01-01	22.9
2008-04-01	23.4
2008-07-01	24.3
2008-10-01	22.6
2009-01-01	19.9
2009-04-01	20.2
2009-07-01	20.2
2009-10-01	19.7
2010-01-01	19
2010-04-01	19.4
2010-07-01	20.4
2010-10-01	20.8
2011-01-01	19.2
2011-04-01	19.9
2011-07-01	20.3
2011-10-01	19.4
2012-01-01	17.9
2012-04-01	18.6
2012-07-01	20.5
2012-10-01	22.2
2013-01-01	20.5
2013-04-01	22.3
2013-07-01	24.3
2013-10-01	25.1
2014-01-01	26.3
2014-04-01	26
2014-07-01	26.7
2014-10-01	26.7
2015-01-01	26.1
2015-04-01	27.6
2015-07-01	29.3
2015-10-01	29.4
2016-01-01	29.7
2016-04-01	31.5
2016-07-01	32.4
2016-10-01	32.3
2017-01-01	31.3
2017-04-01	32.6
2017-07-01	34.1
2017-10-01	33.8
2018-01-01	32.5
2018-04-01	33.5