1964

2.9

2012

5.5

2006

5.5

1975

7.2

2009

7.4

1986

6.5

1939

7.3

1940

7.5

1960

7.4

2007

5.8

1989

5.1

1987

6.8

2011

7.1

1980

6.7

2007

6.8

2012

6.9

2008

6.8

2004

5.8

2004

7.4

1996

6.7