Year	Percent
1986-01-01	76.500
1987-01-01	75.300
1988-01-01	71.650
1989-01-01	69.300
1990-01-01	68.100
1991-01-01	65.575
1992-01-01	64.900
1993-01-01	65.550
1994-01-01	67.200
1995-01-01	69.350
1996-01-01	69.775
1997-01-01	69.250
1998-01-01	67.825
1999-01-01	68.075
2000-01-01	68.950
2001-01-01	69.775
2002-01-01	70.675
2003-01-01	70.450
2004-01-01	71.825
2005-01-01	72.375
2006-01-01	72.875
2007-01-01	73.025
2008-01-01	72.100
2009-01-01	70.075
2010-01-01	69.750
2011-01-01	69.900
2012-01-01	69.050
2013-01-01	69.675
2014-01-01	70.800
2015-01-01	70.700
2016-01-01	71.750
2017-01-01	73.000