1976

8.1

2000

6.3

2004

6.1

1992

4.7

1998

6.3

1948

7.5

1980

7.0

1996

6.1

1984

5.6

2003

5.8

1978

6.6

1975

3.3

1991

6.4

1999

6.4

1974

5.7

1939

5.8

1999

6.1

1968

4.2

1987

5.6

1986

5.0