Year	Percent
1999-01-01	57.500
2000-01-01	58.250
2001-01-01	60.550
2002-01-01	60.400
2003-01-01	63.275
2004-01-01	63.900
2005-01-01	62.750
2006-01-01	63.125
2007-01-01	61.050
2008-01-01	59.925
2009-01-01	60.750
2010-01-01	61.825
2011-01-01	63.200
2012-01-01	64.375
2013-01-01	64.975
2014-01-01	66.450
2015-01-01	67.625
2016-01-01	70.600
2017-01-01	71.575