1972

7.1

1987

8.1

1992

6.7

2001

7.0

1967

7.4

1977

7.7

1968

7.1

1932

6.9

2000

7.0

1942

6.6

2002

7.2

2006

6.7

2005

6.8

1948

6.7

1979

6.4

2009

6.3

1949

6.9

2010

5.9

2010

6.1

2000

5.3