1991

9.1

1995

7.7

1982

9.0

1997

9.3

1980

9.2

1987

8.3

1977

8.6

1971

6.4

1988

7.0

1994

9.2

1992

9.5

1990

8.0

1991

8.5

1981

8.6

1974

5.5

1993

7.8