1973

6.3

1971

6.5

1972

5.6

1968

6.3

1969

7.1

1972

7.0

1969

6.6

1978

5.4

1972

5.7

1971

5.8

1972

5.6

1974

6.2

1970

6.3

1971

6.0

1972

6.2

1971

6.9

1979

6.2

1969

5.9

1970

6.6

1966

6.5

1980

6.2

1971

6.8

1973

3.0

1972

6.8

1970

6.2