Year	Percent
1967	29.94
1968	41.01
1969	38.75
1970	40.74
1973	7.329
1974	4.138
1975	9.583
1976	5.34
1977	2.752
1978	6.441
1979	7.953
1980	12.81
1981	3.293
1982	1.921
1983	10.84
1984	4.834
1985	5.029
1986	4.606
1987	3.424
1988	4.67
1991	0.9383
1992	0.1659
1993	0.2941
1994	0.5564
1995	8.917
1996	7.465
1997	8.482
1998	8.86
1999	9.863
2000	7.885
2001	5.512
2002	4.894
2003	5.865
2004	9.411
2005	12.83
2006	9.572
2007	6.69