1997

6.8

2004

7.6

2007

6.8

1993

5.7

2003

6.1

1973

6.9

2005

7.5

1996

5.9

1969

7.0

2000

6.1

1988

6.3

1972

7.3

1986

6.7

1979

7.5

2003

6.5

1980

7.0

1995

6.2

1992

5.4

1996

6.0

1989

6.8