1971

5.8

1991

4.7

1989

7.6

1992

6.0

2014

7.3

2008

6.5

2006

7.5

1992

7.8

1961

6.2

2004

6.8

1989

6.7

2008

6.8

2004

4.0

1931

8.3

1962

7.9

2000

7.0

2005

7.3

2006

5.0

2004

6.6

2000

7.9