1992

6.4

1978

6.6

1979

7.3

1990

6.9

1995

7.1

1972

5.7

1969

6.2

1994

3.2

2007

5.6

2007

6.5

2006

6.3

2009

4.3

2007

4.4

1968

5.0

1971

4.4

1997

5.0

2002

4.7

1970

4.3

1933

6.3

2004

6.6