Year	% of total
1970	36.61695546873137
1971	36.492091107991726
1972	34.105279440286516
1973	36.62725970214724
1974	35.1689665465579
1975	32.90571803246239
1976	32.16985890932494
1977	23.044091179023344
1978	26.997046549319233
1979	25.380931898429438
1980	34.191240058409065
1981	36.512532321565466
1982	33.72079416719174
1983	34.4664256490507
1984	31.617712040918562
1985	32.48828089569918
1986	37.63494001144175
1987	37.521933467345555
1988	37.87321907837091
1989	38.53164329874145