Quarter	Percent
1999-01-01	35.1
1999-04-01	34.9
1999-07-01	34.7
1999-10-01	35.1
2000-01-01	33.9
2000-04-01	33.1
2000-07-01	33.5
2000-10-01	33.6
2001-01-01	31.7
2001-04-01	30.4
2001-07-01	30.7
2001-10-01	29.9
2002-01-01	28.8
2002-04-01	28.6
2002-07-01	28.4
2002-10-01	28.2
2003-01-01	27.5
2003-04-01	26.7
2003-07-01	27
2003-10-01	26.2
2004-01-01	24.7
2004-04-01	23.3
2004-07-01	23.2
2004-10-01	23.2
2005-01-01	22.3
2005-04-01	21.4
2005-07-01	21.7
2005-10-01	21.9
2006-01-01	21.1
2006-04-01	21.2
2006-07-01	22.1
2006-10-01	21.9
2007-01-01	21.1
2007-04-01	20.9
2007-07-01	21.6
2007-10-01	20.7
2008-01-01	19.8
2008-04-01	19.7
2008-07-01	20.9
2008-10-01	20.5
2009-01-01	17.7
2009-04-01	18.2
2009-07-01	18.5
2009-10-01	18.2
2010-01-01	17.7
2010-04-01	17.8
2010-07-01	18.6
2010-10-01	18.9
2011-01-01	17.6
2011-04-01	18
2011-07-01	18.6
2011-10-01	17.7
2012-01-01	17.1
2012-04-01	17.6
2012-07-01	19.2
2012-10-01	20
2013-01-01	18.4
2013-04-01	19.6
2013-07-01	21
2013-10-01	21.4
2014-01-01	22.6
2014-04-01	23.1
2014-07-01	23.8
2014-10-01	24.6
2015-01-01	23.9
2015-04-01	25.2
2015-07-01	26.7
2015-10-01	26.8
2016-01-01	26.8
2016-04-01	27.4
2016-07-01	29.1
2016-10-01	29.2
2017-01-01	28.4
2017-04-01	28.9
2017-07-01	29.3
2017-10-01	29.3
2018-01-01	27.7
2018-04-01	28.7