1955

7.4

1980

6.8

1968

6.9

2000

7.5

1955

7.2

1985

7.4

1981

6.6

1952

8.3

2002

7.1

1962

7.9

1997

6.2

1977

8.0

2005

5.5

1965

7.2

1958

7.7

1984

7.2

1960

8.0

2007

7.1

1990

6.9

1961

7.9