Year	Percent
1978-01-01	5.30
1979-01-01	5.40
1980-01-01	4.90
1981-01-01	3.80
1982-01-01	3.20
1983-01-01	2.30
1984-01-01	1.90
1985-01-01	1.80
1986-01-01	2.00
1987-01-01	2.00
1988-01-01	2.00
1989-01-01	2.60
1990-01-01	2.50
1991-01-01	2.30
1992-01-01	2.30
1993-01-01	2.60
1994-01-01	2.80
1995-01-01	2.90
1996-01-01	3.00
1997-01-01	3.10
1998-01-01	3.10
1999-01-01	3.10
2000-01-01	3.10
2001-01-01	3.60
2002-01-01	4.00
2003-01-01	4.20
2004-01-01	4.25
2005-01-01	4.20
2006-01-01	4.15
2007-01-01	4.05
2008-01-01	4.05
2009-01-01	4.30
2010-01-01	4.15