Year	Percent
1986-01-01	12.1
1987-01-01	10.9
1988-01-01	9.8
1989-01-01	7.9
1990-01-01	7.8
1991-01-01	8.2
1992-01-01	6.7
1993-01-01	6.5
1994-01-01	7.8
1995-01-01	7.3
1996-01-01	6.3
1997-01-01	6.1
1998-01-01	6.4
1999-01-01	10.1
2000-01-01	9.7
2001-01-01	9.9
2002-01-01	9.8
2003-01-01	9.5
2004-01-01	10.0
2005-01-01	9.2
2006-01-01	7.8
2007-01-01	7.1
2008-01-01	7.8
2009-01-01	10.8
2010-01-01	8.2
2011-01-01	7.1