Year	% of total
1970	56.68506698296936
1971	56.02150523432644
1972	55.44713865992853
1973	55.05620961942397
1974	53.566921195255155
1975	52.96548076609313
1976	53.35492918460433
1977	53.37821621426257
1978	52.45302864384633
1979	50.12586552864219
1980	47.37950528405797
1981	47.480623719088435
1982	48.55155549106591
1983	49.72533539259067
1984	49.75453629375176
1985	49.327700454183194
1986	49.19888038212418
1987	45.79170092176067
1988	46.58340267780125
1989	47.065920706482636