1978

5.8

1975

6.1

1988

5.3

1981

6.0

1991

5.9

1970

5.4

1984

5.6

1979

6.7

1973

5.2

1992

6.5

1968

7.6

1970

6.1

1960

3.2

1958

6.2

1967

7.6