1970

6.2

1993

6.5

1997

6.8

1973

5.7

1983

7.4

1973

6.3

1984

7.2

2006

6.3

1982

7.1

2001

6.1

1982

7.1

1986

6.0

1989

7.1

2001

7.5

2002

6.1

1976

6.7

1967

6.5

1980

6.7

1980

6.6

2004

6.2