Year	Percent
1967	64.93
1968	41.95
1969	30.71
1970	49.44
1971	19.13
1972	18.62
1973	40.84
1974	39.97
1975	40.88
1976	33.34
1977	37.84
1978	37.43
1979	39.76
1980	33.49
1981	22.4
1982	29.01
1983	26.88
1984	13.02
1985	20.95
1986	20.99
1987	23.68
1988	26.38
1989	20.31
1990	21.74
1991	14.35
1992	23.69
1993	18.37
1994	14.06
1995	14.16
1996	15.35
1997	11.74
1998	15.51
1999	6.455
2000	8.009
2001	6.211
2002	7.76
2003	6.024
2004	5.689
2005	6.272
2006	8.822
2007	6.218