1993

6.6

2005

4.5

1985

6.3

2000

7.0

1974

6.2

1989

6.0

1977

7.2

1986

7.0

2002

7.9

2006

7.6

2001

6.6

1987

8.4

2006

7.1

1993

7.4

1992

6.5

2001

7.7

1966

6.4

2000

7.9

2002

7.1

2003

8.7