Year	% of total
1970	87.11397841765243
1971	87.61169079781067
1972	88.1314795645416
1973	88.64632544761972
1974	89.09053411338861
1975	89.20727435914276
1976	88.21929933628188
1977	87.57872700961052
1978	88.2447185184971
1979	88.90749788024387
1980	89.61890486022872
1981	90.2199329798203
1982	90.75561067926908
1983	91.08326177476062
1984	90.21048968344472
1985	90.57734831608454
1986	90.9822235555564
1987	91.11542585350618
1988	91.24942705619293
1989	91.12040799516775