Quarter	Percent
1999-01-01	18.8
1999-04-01	18.8
1999-07-01	18.5
1999-10-01	17.8
2000-01-01	17.3
2000-04-01	17.5
2000-07-01	17.1
2000-10-01	16.6
2001-01-01	16.2
2001-04-01	16.2
2001-07-01	16
2001-10-01	15.9
2002-01-01	16.5
2002-04-01	16.3
2002-07-01	15.8
2002-10-01	15.9
2003-01-01	15.6
2003-04-01	15.4
2003-07-01	14.9
2003-10-01	14.8
2004-01-01	15.5
2004-04-01	15.7
2004-07-01	15.9
2004-10-01	16.5
2005-01-01	17
2005-04-01	17.9
2005-07-01	18.4
2005-10-01	18.2
2006-01-01	18.8
2006-04-01	18.7
2006-07-01	18.8
2006-10-01	18.9
2007-01-01	19.2
2007-04-01	19.6
2007-07-01	19.8
2007-10-01	18.7
2008-01-01	18.4
2008-04-01	18.1
2008-07-01	17.1
2008-10-01	17.9
2009-01-01	19.1
2009-04-01	19.4
2009-07-01	19.4
2009-10-01	19.1
2010-01-01	19.3
2010-04-01	19.4
2010-07-01	18.9
2010-10-01	18.9
2011-01-01	19.5
2011-04-01	19.9
2011-07-01	19.4
2011-10-01	19.6
2012-01-01	19.2
2012-04-01	19.5
2012-07-01	19.5
2012-10-01	20.3
2013-01-01	19.6
2013-04-01	20
2013-07-01	19.2
2013-10-01	19.1
2014-01-01	19.1
2014-04-01	19.6
2014-07-01	20.1
2014-10-01	19.7
2015-01-01	19.5
2015-04-01	19.6
2015-07-01	19.3
2015-10-01	18.5
2016-01-01	17.9
2016-04-01	18.1
2016-07-01	18.6
2016-10-01	19.6
2017-01-01	19.7
2017-04-01	20.7
2017-07-01	19.8
2017-10-01	20.6
2018-01-01	20.1
2018-04-01	20.9