Year	% of total
1970	13.607142776999758
1971	12.077960745463091
1972	11.353244241484763
1973	10.497736202240553
1974	10.314229642006062
1975	10.40509933648584
1976	13.130379206441711
1977	14.115508846390295
1978	14.029213137758271
1979	14.47805420578468
1980	13.807265038086852
1981	13.748295813193002
1982	14.203488194173502
1983	12.18733629579383
1984	12.548764968932534
1985	10.648506186575919
1986	10.271848956496765
1987	10.107665400385669
1988	10.355379142025582
1989	9.805626154567502
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