Year	% of total
1970	12.832876238578258
1971	15.068761730993128
1972	15.761612280730978
1973	17.207753701947905
1974	15.242098136763154
1975	14.859911333373038
1976	12.829911609624563
1977	15.69366501049071
1978	10.715856237240255
1979	8.492856129731408
1980	8.037442706527646
1981	7.456490081432521
1982	10.072395892579895
1983	7.027962305644099
1984	7.076525078432925
1985	3.4160238248790145
1986	2.752838403461007
1987	2.801572980663093
1988	3.0110237637954484
1989	3.145999263682541
1990	0
1991	0
1992	0
1993	0
1994	0
1995	0
1996	0
1997	0
1998	0
1999	0
2000	0
2001	0
2002	0
2003	0
2004	0
2005	0
2006	0
2007	0
2008	0