1974

6.4

1977

7.7

2004

8.0

2005

7.4

1961

7.7

2007

5.4

1976

7.8

1979

7.3

1982

6.9

1985

7.1

1990

5.8

2002

6.3

1988

7.5

2004

6.8

2014

5.8

2017

7.3

1980

7.9

1996

5.7

2003

6.5

1987

6.4