1979

6.9

1959

7.9

1997

7.4

1995

7.7

1979

7.7

2000

7.1

2001

7.9

1990

7.0

1999

8.5

1975

8.4

1995

8.0

1955

7.5

1940

7.9

1983

7.2

1930

7.3

1986

7.9

1972

8.7

1974

8.6

2002

6.7

2005

6.7