Year	Percent
1976-01-01	4.9
1977-01-01	5.7
1978-01-01	6.0
1979-01-01	5.4
1980-01-01	5.3
1981-01-01	5.5
1982-01-01	8.2
1983-01-01	9.2
1984-01-01	9.0
1985-01-01	8.4
1986-01-01	7.7
1987-01-01	7.2
1988-01-01	6.4
1989-01-01	6.3
1990-01-01	6.7
1991-01-01	8.6
1992-01-01	9.4
1993-01-01	9.6
1994-01-01	8.5
1995-01-01	7.6
1996-01-01	7.7
1997-01-01	7.1
1998-01-01	6.4
1999-01-01	5.7
2000-01-01	5.0
2001-01-01	5.4
2002-01-01	5.9
2003-01-01	5.7
2004-01-01	5.3
2005-01-01	5.0
2006-01-01	4.5
2007-01-01	4.3
2008-01-01	4.3
2009-01-01	6.1
2010-01-01	5.9
2011-01-01	5.4
2012-01-01	5.1