1977

6.2

1974

4.8

1975

5.7

1975

6.2

1984

7.2

1981

6.5

1984

3.9

1991

5.4

1992

5.6

1992

5.3

1972

6.6

1972

6.6

1985

7.5

1985

6.4

1985

7.1

1971

6.4

1987

6.5

1969

5.2

1975

6.7

1976

6.3

1988

6.0

1980

5.3

1973

6.4

1984

6.3

1974

7.2

1971

3.8