1981

4.6

2007

6.8

1977

5.4

2000

6.1

2008

3.1

1951

6.0

1986

5.2

1965

7.0

1956

7.2

1996

9.0

2009

6.6

1940

7.3

2006

7.4

2007

4.3

1989

3.2

1996

5.8

2003

5.6

2005

6.8

1974

4.7