1968

8.1

1995

7.6

1985

7.7

2005

6.5

1996

6.4

1982

7.9

1994

8.3

1987

7.5

1932

7.8

1988

7.9

2001

7.2

1990

6.3

2002

7.2

2004

7.4

1971

8.2

1998

6.4

2006

6.4

2005

6.6

2008

6.0

1920

7.9