1960

4.2

1973

7.7

2003

5.7

2001

6.3

1996

7.2

1977

4.5

1990

6.3

2008

5.6

2003

6.0

2008

5.0

1983

6.1

2008

6.6

2006

6.6

2007

6.1

2004

5.4

1980

7.0

1970

7.5

1979

6.3

1984

6.8

1967

5.8