1976

6.6

1980

6.7

1990

6.1

2008

5.8

1980

5.3

1981

5.4

2003

6.0

1983

5.5

1993

6.2

1990

6.4

1999

6.0

1985

5.4

2004

3.7

1986

6.8

1998

6.4

1990

7.1

1967

7.3

1984

6.8

1997

5.2

1994

6.2