1960

8.4

2005

7.0

1998

6.9

1972

7.1

2004

7.3

2007

6.4

2005

7.1

1997

7.1

1999

7.0

2002

6.7

1963

7.5

2005

6.3

1972

7.1

1975

7.7

1978

6.0

1987

4.1

1990

7.8

2003

7.8