1985

6.2

1984

6.2

1985

6.7

1988

7.8

1995

7.4

2006

5.9

1975

7.3

1953

8.0

2006

7.5

1995

7.3

1990

7.0

2005

6.8

1997

6.8

2001

4.7

2004

6.1

1986

6.5

2002

6.7

1991

6.7

1931

7.5

1966

6.3