1954

7.5

1960

6.2

2001

6.9

1992

7.0

2000

5.9

2000

7.1

2004

7.9

1998

8.3

1987

7.3

1983

8.2

1999

7.7

1955

7.4

1988

5.1

1971

6.8

1991

7.1

1989

7.1

2000

6.0

2002

8.0

1993

6.2

2002

6.6