Year	Percent
1982-01-01	12.9
1983-01-01	13.9
1984-01-01	15.5
1985-01-01	16.8
1986-01-01	16.8
1987-01-01	16.6
1988-01-01	16.2
1989-01-01	14.7
1990-01-01	13.4
1991-01-01	14.7
1992-01-01	15.4
1993-01-01	15.6
1994-01-01	14.4
1995-01-01	12.3
1996-01-01	11.7
1997-01-01	9.9
1998-01-01	7.6
1999-01-01	5.7
2000-01-01	4.2
2001-01-01	3.9
2002-01-01	4.5
2003-01-01	4.6
2004-01-01	4.5
2005-01-01	4.4
2006-01-01	4.5
2007-01-01	4.6
2008-01-01	6.3
2009-01-01	11.9
2010-01-01	13.7
2011-01-01	14.5