1973

7.1

1954

5.5

1980

5.0

1993

5.5

1998

7.0

1965

6.2

1984

6.5

1975

6.9

1997

7.4

1977

5.8

1996

5.8

1999

7.5

1990

6.9

2005

8.1

1986

5.7

1995

5.0

2014

8.1

2015

7.0

2015

6.1

2012

6.0