Year	Percent
1983	9
1984	9.12
1985	8.52
1986	7.86
1987	7.15
1988	6.59
1989	5.77
1990	5.51
1991	5
1992	4.92
1993	4.38
1994	4.22
1995	3.78
1996	3.41
1997	3.22
1998	2.87
1999	2.79
2000	2.31
2001	2.04
2002	1.96
2003	2.01
2004	1.85
2005	1.54
2006	1.45
2007	1.05
2008	0.99
2009	1.01
2010	0.85
2011	0.82
2012	0.7
2013	0.7
2014	0.7
2015	0.64
2016	0.65
2017	0.55