1961

6.9

1988

5.5

2004

7.2

2007

6.5

1988

6.2

1998

6.0

2012

5.2

1994

5.7

2008

7.0

1991

5.2

1997

6.2

2013

6.3

1966

6.2

1975

6.8

2005

6.7

2017

6.6

2005

7.8

2010

6.4

1920

7.3

1987

7.3