1968

6.7

1998

7.0

2004

8.0

2006

7.9

2004

8.0

2005

7.3

2002

7.1

1991

6.6

1999

6.8

1993

7.1

1979

6.2

2004

6.3

2005

8.1

1974

5.3

2000

6.5

1997

6.6

2003

5.5

1998

8.5

1996

9.5

1996

3.5