1975

6.7

1998

8.2

2005

5.1

2008

6.1

1991

6.7

1980

6.3

2005

4.9

1993

7.3

1970

7.5

1955

7.3

2017

8.8

2002

6.2

1989

6.7

1986

6.2

2005

6.4

1988

6.8

2009

6.1

2009

5.9

2000

1.5

2004

7.6