1989

7.2

2002

6.3

1990

7.7

1973

8.0

1998

7.9

1985

6.5

2004

7.6

1996

7.4

1981

8.0

1984

7.3

1998

7.2

1992

7.5

1995

6.5

1998

7.4

1960

7.6

2002

6.9

1999

6.2

2005

7.2

1987

7.0

2007

6.8