1990

6.2

1992

6.2

2006

4.7

1994

6.5

1971

7.2

1983

5.9

2007

6.2

2008

6.6

2007

6.5

2004

7.0

2005

5.4

1999

6.8

1990

6.4

1997

6.8

1998

5.8

1932

7.4

2000

6.9

1968

7.1

1946

6.9

1987

7.3