Year	% of total
1970	65.74128288130275
1971	66.18246213905171
1972	65.66621886175648
1973	65.22089622708445
1974	64.82140143451554
1975	64.88689464087541
1976	63.90382146235979
1977	61.64835548074274
1978	62.22991049755684
1979	61.14990215623134
1980	55.981901546485226
1981	50.18288339140082
1982	55.265675201285966
1983	55.17237325788745
1984	57.476807723911264
1985	56.727064298325956
1986	58.18262102115664
1987	57.0763817953708
1988	54.07100927032017
1989	54.32808483546218