Year	% of total
1970	15.8643596010722
1971	15.857409670818628
1972	13.69453907175803
1973	14.456820524981673
1974	13.634229279399154
1975	13.918118807578653
1976	12.247289645788525
1977	12.626216206310318
1978	12.127092501835497
1979	14.227442071890655
1980	13.798462141247919
1981	15.841940692518646
1982	15.24342667165843
1983	13.458266845788843
1984	13.087360129524987
1985	14.37540667611753
1986	16.636353534885874
1987	16.634043144153317
1988	21.402571328184937
1989	19.43352322033424