1977

6.8

1985

6.2

1987

6.5

1991

7.6

1984

6.2

1999

7.0

1982

7.5

1985

6.7

2000

6.5

2001

6.9

1988

7.8

2005

7.1

1998

6.8

1992

8.1

2006

5.9

1994

6.2

1995

7.3

1990

7.0

2005

6.7

2007

6.1