1988

7.8

2005

7.1

1996

7.0

1977

6.8

1985

6.2

1997

7.0

1985

7.7

1985

8.3

2005

6.7

1972

6.0

1994

6.2

1973

6.5

2000

6.5

2001

6.9

1995

7.3

1990

7.0

1994

7.1

1991

6.5

2002

5.7

2005

6.1