1980

6.0

1994

5.8

1971

8.1

1986

6.7

1990

6.9

1988

5.8

1991

6.6

1992

6.8

1991

7.4

1988

6.4

1992

6.7

1987

7.7

1997

7.2

1996

7.0

1978

0.0

2000

2.0

1985

7.5