1990

6.2

1991

6.8

1992

6.2

2006

4.7

1971

7.2

1993

6.3

1983

5.9

1981

7.1

2008

6.6

2007

6.5

2004

7.0

2005

5.4

1999

6.8

1997

6.8

1997

6.9

1932

7.4

2000

6.9

1968

7.1

1987

7.3

1989

7.0