Year	Percent
1960-01-01	5.75
1961-01-01	5.50
1962-01-01	5.75
1963-01-01	5.75
1964-01-01	5.75
1965-01-01	6.00
1966-01-01	6.00
1967-01-01	6.50
1968-01-01	6.75
1969-01-01	8.50
1970-01-01	7.50
1971-01-01	6.00
1972-01-01	6.00
1973-01-01	9.50
1974-01-01	11.00
1975-01-01	9.75
1976-01-01	9.25
1977-01-01	8.25
1978-01-01	11.50
1979-01-01	15.00
1980-01-01	18.25
1981-01-01	17.25
1982-01-01	12.50
1983-01-01	11.00
1984-01-01	11.25
1985-01-01	10.00
1986-01-01	9.75
1987-01-01	9.75
1988-01-01	12.25
1989-01-01	13.50
1990-01-01	12.75
1991-01-01	8.00
1992-01-01	7.25
1993-01-01	5.50
1994-01-01	8.00
1995-01-01	7.50
1996-01-01	4.75
1997-01-01	6.00
1998-01-01	6.75
1999-01-01	6.50
2000-01-01	7.50
2001-01-01	4.00
2002-01-01	4.50
2003-01-01	4.50
2004-01-01	4.25
2005-01-01	5.00
2006-01-01	6.00
2007-01-01	6.00
2008-01-01	3.50
2009-01-01	2.25
2010-01-01	3.00
2011-01-01	3.00
2012-01-01	3.00
2013-01-01	3.00
2014-01-01	3.00
2015-01-01	2.70
2016-01-01	2.70
2017-01-01	3.20