1984

7.3

1998

7.2

1973

5.7

1993

8.0

1992

7.6

2000

7.0

1997

8.1

1995

6.5

2004

8.6

1960

7.6

2006

1.0

2005

7.1

2002

6.9

1999

6.1

2001

8.2

2005

7.2

1987

7.1

2007

6.7

1988

5.2

1966

7.5