Year	Percent
1983-01-01	13.875
1984-01-01	15.500
1985-01-01	16.825
1986-01-01	16.850
1987-01-01	16.625
1988-01-01	16.200
1989-01-01	14.725
1990-01-01	13.450
1991-01-01	14.775
1992-01-01	15.400
1993-01-01	15.650
1994-01-01	14.375
1995-01-01	12.275
1996-01-01	11.650
1997-01-01	9.875
1998-01-01	7.575
1999-01-01	5.775
2000-01-01	4.350
2001-01-01	3.925
2002-01-01	4.450
2003-01-01	4.750
2004-01-01	4.525
2005-01-01	4.350
2006-01-01	4.425
2007-01-01	5.025
2008-01-01	6.775
2009-01-01	12.650
2010-01-01	14.575
2011-01-01	15.375
2012-01-01	15.525
2013-01-01	13.800
2014-01-01	11.925
2015-01-01	9.975
2016-01-01	8.425
2017-01-01	6.750