Year	Percent
1999-01-01	56.875
2000-01-01	56.075
2001-01-01	56.950
2002-01-01	55.825
2003-01-01	55.125
2004-01-01	54.700
2005-01-01	52.075
2006-01-01	51.825
2007-01-01	52.125
2008-01-01	52.275
2009-01-01	54.975
2010-01-01	57.350
2011-01-01	59.075
2012-01-01	60.975
2013-01-01	62.225
2014-01-01	64.275
2015-01-01	65.300
2016-01-01	66.975
2017-01-01	66.650