Year	% of total
1970	3.74539486889743
1971	3.7503802738746526
1972	3.949852099219342
1973	4.704414034857818
1974	5.505168612479839
1975	5.377609187663835
1976	5.140153638213281
1977	4.79368800965976
1978	4.19511273143964
1979	4.238340515477977
1980	8.048366843585157
1981	7.724067662311937
1982	6.134320436172748
1983	4.757749819072538
1984	4.33733243997345
1985	3.930197572591796
1986	4.512841755913564
1987	4.150791439059502
1988	4.355844717493324
1989	5.126834068931167