1970

0.0

1989

6.7

1988

5.1

2005

6.9

2008

7.4

1983

6.1

1993

7.1

1998

5.7

2008

6.7

1977

5.7

1993

5.6

2007

6.5

1981

6.6

1982

0.0

1995

7.5