1991

9.1

1995

7.6

1982

9.0

1997

9.3

1980

9.2

1987

8.3

1977

8.5

1971

6.2

1988

7.2

1994

9.2

1992

9.5

1990

8.5

1991

9.3

1981

8.6

1974

5.5

1993

7.8