Year	Percent
1971	8.462
1972	10.08
1973	9.189
1974	9.594
1975	8.766
1976	11.36
1977	11.41
1978	12.32
1979	8.611
1980	9.208
1981	12.95
1982	10.53
1983	9.817
1984	10.72
1985	9.045
1986	7.337
1987	6.567
1988	6.04
1989	6.756
1990	6.215
1991	4.637
1992	3.857
1993	0
1994	0
1995	0
1996	0
1997	0
1998	0
1999	0
2000	0
2001	0
2002	0
2003	0
2004	0
2005	0
2006	0
2007	0
2008	0
2009	0
2010	0