Year	Percent
1986-01-01	54.625
1987-01-01	54.800
1988-01-01	54.200
1989-01-01	52.975
1990-01-01	53.975
1991-01-01	54.275
1992-01-01	53.950
1993-01-01	53.975
1994-01-01	54.975
1995-01-01	55.850
1996-01-01	57.250
1997-01-01	57.100
1998-01-01	56.950
1999-01-01	57.250
2000-01-01	57.350
2001-01-01	58.225
2002-01-01	59.000
2003-01-01	59.300
2004-01-01	59.725
2005-01-01	60.850
2006-01-01	61.325
2007-01-01	61.700
2008-01-01	62.225
2009-01-01	61.950
2010-01-01	61.700
2011-01-01	62.050
2012-01-01	62.475
2013-01-01	62.550
2014-01-01	63.450
2015-01-01	63.400
2016-01-01	64.500
2017-01-01	65.450