Year	Percent
1973-01-01	53.4
1974-01-01	53.5
1975-01-01	54.5
1976-01-01	54.1
1977-01-01	54.2
1978-01-01	54.0
1979-01-01	54.2
1980-01-01	55.4
1981-01-01	56.7
1982-01-01	56.6
1983-01-01	55.7
1984-01-01	55.7
1985-01-01	55.5
1986-01-01	56.0
1987-01-01	55.2
1988-01-01	55.9
1989-01-01	56.1
1990-01-01	57.0
1991-01-01	57.7
1992-01-01	58.2
1993-01-01	57.4
1994-01-01	58.0
1995-01-01	59.6
1996-01-01	60.1
1997-01-01	61.1
1998-01-01	61.7
1999-01-01	62.4
2000-01-01	63.4
2001-01-01	64.1
2002-01-01	64.8
2003-01-01	64.8
2004-01-01	65.0
2005-01-01	64.9
2006-01-01	65.2
2007-01-01	66.0
2008-01-01	66.2
2009-01-01	66.2
2010-01-01	64.6
2011-01-01	64.2
2012-01-01	64.8