Year	Percent
1960-01-01	4.50
1961-01-01	4.50
1962-01-01	2.35
1963-01-01	2.46
1964-01-01	4.50
1965-01-01	5.00
1966-01-01	6.00
1967-01-01	6.00
1968-01-01	5.50
1969-01-01	5.50
1970-01-01	5.50
1971-01-01	6.50
1972-01-01	6.00
1973-01-01	3.78
1974-01-01	6.48
1975-01-01	7.42
1976-01-01	8.28
1977-01-01	8.41
1978-01-01	7.87
1979-01-01	4.70
1980-01-01	6.54
1981-01-01	14.54
1982-01-01	14.35
1983-01-01	17.75
1984-01-01	20.75
1985-01-01	13.00
1986-01-01	9.50
1987-01-01	9.50
1988-01-01	14.50
1989-01-01	18.00
1990-01-01	18.00
1991-01-01	17.00
1992-01-01	14.00
1993-01-01	12.00
1994-01-01	13.00
1995-01-01	15.00
1996-01-01	17.00
1997-01-01	16.00
1998-01-01	19.32
1999-01-01	12.00
2000-01-01	12.00
2001-01-01	9.50
2002-01-01	13.50
2003-01-01	8.00
2004-01-01	7.50
2005-01-01	7.00
2006-01-01	9.00
2007-01-01	11.00
2008-01-01	11.50
2009-01-01	7.00
2010-01-01	5.50
2011-01-01	5.50
2012-01-01	5.00
2013-01-01	5.00
2014-01-01	5.75
2015-01-01	6.25
2016-01-01	7.00
2017-01-01	6.75