1966    .         0.126    .    .
1967    .         0.278    .    .
1968     2.630    0.061    .    .
1969     3.052    0.035    .    .
1970     3.842    0.120    .    .
1971     5.670    0.406    .    .
1972    10.716    0.578    .    .
1973    20.366    0.449    .    .
1974    29.551    0.712    .    .
1975    16.917    0.225    .    .
1976    19.718    0.303    .    .
1977    14.374    0.197    .    .
1978    10.270    0.337    .    .
1979     9.234    0.478    .    .
1980    13.888    0.524    .    .
1981    27.698    0.796    .    .
1982    29.352    0.093    .    .
1983    10.832    0.953    .    .
1984    11.642    0.923    .    .
1985    11.853    0.719    .    .
1986    19.705    1.018    .    .
1987    22.283    0.876    .    .
1988    22.839    1.267    .    .
1989    15.119    .        .    .
1990    .         .        .    .