Year	Percent
1967	42.16
1968	28.74
1969	22.17
1970	43.44
1971	27.32
1972	7.477
1973	48.06
1974	57.82
1975	85.24
1976	89.87
1977	57.87
1978	46.75
1979	55.09
1980	47.74
1981	57.46
1982	38.85
1983	45.52
1984	18.82
1985	35.99
1986	30.78
1987	41.04
1988	16
1989	20.92
1990	28.67
1991	22.46
1992	30.01
1993	25.7
1994	25.15
1995	22.4
1996	21.76
1997	19.18
1998	20.92
1999	24.18
2000	23.5
2001	17.6
2002	15.43
2003	11.56
2004	9.374
2005	9.132
2006	7.573
2007	5.247