1985

7.1

2008

6.2

2002

6.1

2007

5.6

2003

5.7

1997

6.1

2001

6.1

2003

6.1

1968

6.5

2005

4.9

1996

6.0

1983

6.5

1933

7.5

2006

5.5

1981

6.7

1990

6.4

1997

6.2

2003

6.2

1954

6.8

2004

5.3