Year	Percent
1983-01-01	14.435
1984-01-01	13.710
1985-01-01	14.350
1986-01-01	14.005
1987-01-01	13.715
1988-01-01	14.540
1989-01-01	12.590
1990-01-01	11.175
1991-01-01	11.320
1992-01-01	9.330
1993-01-01	8.840
1994-01-01	8.750
1995-01-01	6.675
1996-01-01	8.080
1997-01-01	8.980
1998-01-01	9.045
1999-01-01	17.260
2000-01-01	15.775
2001-01-01	16.535
2002-01-01	16.930
2003-01-01	16.510
2004-01-01	17.045
2005-01-01	17.530
2006-01-01	18.890
2007-01-01	22.105
2008-01-01	17.465
2009-01-01	20.955
2010-01-01	20.670
2011-01-01	19.830
2012-01-01	20.240
2013-01-01	20.005
2014-01-01	18.990
2015-01-01	18.615