Year	Percent
1978-12-31	12.625
1979-12-31	16.565
1980-12-31	14.47
1981-12-31	15.72
1982-12-31	10.44
1983-12-31	9.695
1984-12-31	10.22
1985-12-31	11.91
1986-12-31	11.19
1987-12-31	9.065
1988-12-31	13.095
1989-12-31	15.09
1990-12-31	13.375
1991-12-31	10.97
1992-12-31	6.88
1993-12-31	5.265
1994-12-31	7.075
1995-12-31	6.345
1996-12-31	6.66
1997-12-31	7.595
1998-12-31	5.825
1999-12-31	6.2188
2000-12-31	5.7813
2001-12-31	4.0469
2002-12-31	3.915
2003-12-31	4.11
2004-12-31	4.85
2005-12-31	4.53
2006-12-31	5.385
2007-12-31	5.86
2008-12-31	3
2009-12-31	0.825
2010-12-31	1.045
2011-12-31	1.395
2012-12-31	0.665
2013-12-31	0.585
2014-12-31	0.675
2015-12-31	0.79
2016-12-31	0.565