Quarter	Percent
1999-01-01	19.1
1999-04-01	18.8
1999-07-01	18.7
1999-10-01	18.7
2000-01-01	19.2
2000-04-01	20
2000-07-01	20.5
2000-10-01	20.9
2001-01-01	21.7
2001-04-01	21.4
2001-07-01	21.6
2001-10-01	22.1
2002-01-01	22
2002-04-01	22.6
2002-07-01	22.1
2002-10-01	22.7
2003-01-01	23.1
2003-04-01	23.7
2003-07-01	23.8
2003-10-01	24.4
2004-01-01	24.8
2004-04-01	24.8
2004-07-01	24.7
2004-10-01	25.5
2005-01-01	26.8
2005-04-01	27.6
2005-07-01	27.7
2005-10-01	28.5
2006-01-01	29.2
2006-04-01	28.9
2006-07-01	28.1
2006-10-01	29.5
2007-01-01	29.9
2007-04-01	30.5
2007-07-01	29.7
2007-10-01	30.7
2008-01-01	30.8
2008-04-01	31.4
2008-07-01	31
2008-10-01	31.5
2009-01-01	31.7
2009-04-01	32.4
2009-07-01	32.1
2009-10-01	32.4
2010-01-01	32.6
2010-04-01	32.5
2010-07-01	33.2
2010-10-01	34.1
2011-01-01	34.4
2011-04-01	36.1
2011-07-01	36.3
2011-10-01	35.9
2012-01-01	35.5
2012-04-01	36.2
2012-07-01	36.5
2012-10-01	35.8
2013-01-01	35.3
2013-04-01	36.2
2013-07-01	36.6
2013-10-01	37.1
2014-01-01	37.3
2014-04-01	37.4
2014-07-01	37.6
2014-10-01	38.9
2015-01-01	39.4
2015-04-01	39.8
2015-07-01	39.7
2015-10-01	41.7
2016-01-01	42.2
2016-04-01	42.4
2016-07-01	43.1
2016-10-01	43.2
2017-01-01	43.3
2017-04-01	43.5
2017-07-01	43.3
2017-10-01	44.1
2018-01-01	43.9
2018-04-01	45.0
2018-07-01	45.2