Year	Percent
1967	39.91
1968	21.14
1969	19.43
1970	28.37
1971	9.788
1972	11.9
1973	9.992
1974	18.46
1975	14.65
1976	14.07
1977	12.46
1978	14.42
1979	14.28
1980	18.09
1981	13.82
1982	17.08
1983	17.83
1984	21.77
1985	21.86
1986	25.51
1987	16.73
1988	27.31
1989	23.88
1990	19.73
1991	21.49
1992	17.94
1993	17.2
1994	11.88
1995	12.93
1996	13.08
1997	11.96
1998	14.36
1999	11.12
2000	7.406
2001	11.95
2002	7.272
2003	12.1
2004	11.68
2005	22.56
2006	13.67
2007	13.65