Year	Percent
1967	30.44
1968	39
1969	69.63
1970	63.32
1971	51.9
1972	48.89
1973	52.27
1974	36.96
1975	19.61
1976	23.68
1977	41.78
1978	49
1979	49.76
1980	14.35
1981	28.25
1982	24.43
1983	15.66
1984	52.08
1985	17.4
1986	33.71
1987	37.65
1988	31.19
1989	14.88
1990	30.2
1991	23.42
1992	25.11
1993	26.41
1994	30.64
1995	27.9
1996	17.17
1997	16.17
1998	14.27
1999	12.15
2000	8.459
2001	10.3
2002	5.405
2003	6.778
2004	5.432
2005	7.645
2006	4.597
2007	9.93