Year	% of total
1970	38.676854027187424
1971	38.4068734749838
1972	38.18121629773769
1973	38.45376855952403
1974	38.43025175753655
1975	38.48919680919559
1976	26.763591630688733
1977	25.551288318634242
1978	13.325367829731515
1979	11.690086085779242
1980	11.343024803934869
1981	9.905148181222314
1982	9.137460663376078
1983	9.624159675478468
1984	8.940312514849603
1985	8.015424090824386
1986	10.738183472182323
1987	7.886370253296176
1988	6.549218972363204
1989	6.02934056837559