Year	Percent
1999-01-01	59.775
2000-01-01	60.150
2001-01-01	59.600
2002-01-01	59.700
2003-01-01	60.575
2004-01-01	60.475
2005-01-01	61.350
2006-01-01	62.050
2007-01-01	61.650
2008-01-01	61.175
2009-01-01	61.225
2010-01-01	61.900
2011-01-01	62.375
2012-01-01	63.700
2013-01-01	64.700
2014-01-01	66.975
2015-01-01	68.650
2016-01-01	70.125
2017-01-01	71.175