1988

6.2

1993

6.2

2009

7.6

2010

6.1

2005

5.2

1989

7.5

2008

5.2

1984

9.2

1940

6.3

2007

6.5

1991

5.7

2005

5.3

1973

6.5

2013

7.1

1975

6.8

2012

6.7

2001

6.6

2002

4.5

2008

6.9

1966

6.2