Year	Percent
1971	69.34
1972	64.01
1973	9.969
1975	7.755
1976	6.188
1978	7.5
1979	6.991
1980	11.9
1981	10.45
1982	5.913
1983	7.089
1984	11.37
1985	10.9
1986	10.36
1987	11.84
1988	12.6
1989	13.69
1990	11.25
1991	11.22
1992	11.22
1993	11.22
1994	7.992
1995	8.465
1996	8.409
1997	4.702
1998	3.038
1999	5.747
2000	3.737
2001	5.606
2002	3.693
2003	2.339
2004	3.208
2005	3.666
2006	2.829
2007	4.519