Year	Percent
1967	51.4
1968	92.29
1969	81.07
1970	69.3
1971	35.26
1972	38.85
1973	30.51
1974	36.99
1975	56.44
1976	46.55
1977	50.05
1978	50.76
1979	41.84
1980	58.35
1981	40.71
1982	54.03
1983	50.17
1984	35.63
1985	44.39
1986	45.23
1987	61.42
1988	50.93
1989	46.37
1990	42.95
1991	63.22
1992	39.39
1993	49.12
1994	50.17
1995	53.41
1996	48.58
1997	53.13
1998	50.97
1999	45.54
2000	45.78
2001	47.64
2002	48.6
2003	44.74
2004	48.56
2005	43.26
2006	42.62
2007	34.64