1980 7.0

1980 6.2

1980 4.6

1979 6.4

1979 8.7

1978 6.9

1978 7.3

1977 5.2

1977 6.6

1976 7.9

1976 6.6

1976 7.5

1975 7.4

1975 7.3

1975 7.4

1974 7.2

1974 8.1

1974 7.7

1973 7.0

1972 7.9