1967

5.5

2003

6.8

2000

6.0

1995

6.5

1980

5.6

2002

7.0

1990

6.1

1990

6.7

2002

6.2

1996

5.4

1996

6.2

1997

6.3

1998

6.8

1998

7.1

2006

4.8

2003

6.8

1988

6.6

1933

5.0

1929

5.8

2002

6.4