Year	Percent
1967	40.83
1968	47.53
1969	30.62
1970	19.01
1971	10.59
1972	18.44
1973	32.33
1974	20.93
1975	18.39
1976	18.27
1977	34.22
1978	23.24
1979	21.02
1980	20.88
1981	34.87
1982	44.46
1983	25.27
1984	18.4
1985	24.35
1986	29.47
1987	21.27
1988	19.68
1989	25.88
1990	23.69
1991	27.45
1992	14.91
1993	11.76
1994	11.8
1995	5.775
1996	9.089
1997	8.72
1998	13.46
1999	11.99
2000	9.456
2001	11.3
2002	9.812
2003	9.768
2004	9.298
2005	9.428
2006	6.688
2007	6.671