Year	% of total
1970	93.66891214805618
1971	93.41089416245634
1972	93.23314342349782
1973	93.1761135633537
1974	93.04321507614858
1975	93.4414078182578
1976	93.40861201831333
1977	93.5973415525478
1978	93.39495332909276
1979	93.582303818204
1980	94.56671517725059
1981	96.31502773330747
1982	92.54716660278855
1983	92.6492198621545
1984	92.65979770858131
1985	92.58984683835054
1986	92.5629221012363
1987	92.49751000364893
1988	92.41657901732044
1989	92.60292982191068