Year	Percent
1967	53.16
1968	58.53
1969	55.61
1970	52.15
1971	14.52
1972	11.42
1973	38.76
1975	45.63
1976	49
1978	40.89
1979	49.51
1980	57.94
1981	51.18
1982	58.9
1983	53.74
1984	17.76
1985	37.05
1986	39.47
1987	31.38
1988	39.32
1989	34.07
1990	22.79
1991	22.73
1992	22.73
1993	22.73
1994	18.35
1995	25.51
1996	25.54
1997	8.545
1998	7.856
1999	4.351
2000	7.126
2001	10.78
2002	11.21
2003	9.9
2004	8.787
2005	9.848
2006	7.467
2007	8.763