Year	Percent
1970-01-01	62.1
1971-01-01	62.2
1972-01-01	62.3
1973-01-01	62.6
1974-01-01	63.0
1975-01-01	63.2
1976-01-01	62.7
1977-01-01	62.7
1978-01-01	61.9
1979-01-01	61.6
1980-01-01	62.1
1981-01-01	61.9
1982-01-01	61.7
1983-01-01	61.4
1984-01-01	61.5
1985-01-01	61.7
1986-01-01	62.8
1987-01-01	63.0
1988-01-01	63.3
1989-01-01	64.2
1990-01-01	64.7
1991-01-01	64.2
1992-01-01	63.9
1993-01-01	63.6
1994-01-01	63.9
1995-01-01	64.6
1996-01-01	64.6
1997-01-01	64.3
1998-01-01	64.3
1999-01-01	64.0
2000-01-01	64.4
2001-01-01	64.4
2002-01-01	64.3
2003-01-01	64.6
2004-01-01	64.6
2005-01-01	65.4
2006-01-01	65.8
2007-01-01	66.2
2008-01-01	66.7
2009-01-01	66.7
2010-01-01	66.4
2011-01-01	66.5
2012-01-01	66.2