Year	Percent
1980-01-01	5.00
1981-01-01	4.00
1982-01-01	4.00
1983-01-01	4.00
1984-01-01	4.00
1985-01-01	4.00
1986-01-01	4.00
1987-01-01	6.00
1988-01-01	6.00
1989-01-01	7.00
1990-01-01	7.00
1991-01-01	7.00
1992-01-01	7.07
1993-01-01	5.45
1994-01-01	5.00
1995-01-01	4.50
1996-01-01	5.50
1997-01-01	4.05
1998-01-01	3.90
1999-01-01	3.98
2000-01-01	3.90
2001-01-01	4.10
2002-01-01	4.90
2003-01-01	5.50
2004-01-01	5.60
2005-01-01	6.20
2006-01-01	6.70
2007-01-01	6.20
2008-01-01	5.30
2009-01-01	5.10
2010-01-01	4.10
2011-01-01	4.60
2012-01-01	4.60
2013-01-01	4.90
2014-01-01	4.60
2015-01-01	5.00
2016-01-01	6.00