1984

7.3

1992

6.8

1998

7.2

1973

5.4

2000

6.2

1995

7.6

1993

8.0

2004

8.3

1992

7.5

2000

7.0

1981

5.5

1997

8.1

1995

6.5

2004

8.6

1998

7.4

1960

7.6

2006

1.0

2005

7.1

2002

6.9

1999

6.2