1979

6.5

2009

7.4

2008

6.2

1997

6.6

1985

5.4

1967

5.2

2001

5.3

1976

6.6

1982

7.5

1984

6.6

1986

7.2

1989

5.7

1991

7.0

1994

6.5

1996

7.3

1998

6.4

2002

6.3

2006

6.9

1993

5.5

1992

5.2