Year	Percent
1986-01-01	66.725
1987-01-01	66.275
1988-01-01	64.875
1989-01-01	63.600
1990-01-01	63.850
1991-01-01	63.850
1992-01-01	63.325
1993-01-01	63.325
1994-01-01	64.075
1995-01-01	64.725
1996-01-01	65.650
1997-01-01	65.475
1998-01-01	65.050
1999-01-01	65.075
2000-01-01	65.200
2001-01-01	65.775
2002-01-01	66.525
2003-01-01	66.300
2004-01-01	66.825
2005-01-01	67.700
2006-01-01	68.175
2007-01-01	68.375
2008-01-01	68.500
2009-01-01	68.000
2010-01-01	67.700
2011-01-01	67.900
2012-01-01	67.900
2013-01-01	67.850
2014-01-01	68.725
2015-01-01	68.725
2016-01-01	69.775
2017-01-01	70.725