| Year | Value | | 1994 | 0.00067460906404738 | | 1993 | 0.00076408787010506 | | 1992 | 0.00090339133105678 | | 1987 | 0.079284326809996 | | 1985 | 0.088784977581794 | | 1984 | 0.13470122954029 | | 1983 | 0.13247732599613 | | 1982 | 0.16174518911745 | | 1981 | 0.16832655351382 | | 1974 | 0.15525823096945 | | 1973 | 0.29156185684885 | | 1972 | 0.59502473295577 |
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