1997

6.8

2007

7.2

2001

6.3

2007

7.3

1968

4.9

1967

6.4

1993

7.5

1997

6.0

2005

6.7

2006

5.2

2005

7.7

1976

6.4

1994

6.2

2008

6.3

1957

6.4

2003

7.4

2004

7.5

1991

6.8

1998

6.3

1972

6.2