Year	Percent
1967	4.74
1968	27.75
1969	71.72
1970	17.08
1971	10.1
1972	20.64
1973	2.474
1974	3.294
1975	4.422
1976	5.552
1977	8.378
1978	10.33
1979	4.613
1980	3.004
1981	8.52
1982	10.2
1983	9.422
1984	23.57
1985	33.55
1986	37.01
1987	21.07
1988	18.34
1989	40.06
1990	24.03
1991	16.9
1992	18.89
1993	20.07
1994	19.08
1995	17.06
1996	19.87
1997	23.27
1998	16.61
1999	17.01
2000	17.85
2001	18.22
2002	11.81
2003	18.41
2004	13.8
2005	10.8
2006	9.737
2007	11.49