1980

7.2

1987

7.5

2005

7.5

1986

6.7

1991

7.3

2006

7.4

1993

7.7

1998

7.3

2006

4.7

1986

6.4

1998

7.4

1966

7.9

1940

4.3

1990

7.3

2002

7.0

1981

6.8

1976

4.0

1993

6.7

2006

6.3

1997

6.5