1981

7.9

1989

7.8

1952

7.0

1997

6.1

2005

4.9

1954

6.8

1991

7.3

1968

7.5

1991

6.5

2005

5.9

1997

6.2

2003

6.2

1980

5.3

1971

7.0

2003

6.3

1976

6.6

1990

6.1

1944

5.5

2010

3.9

2014

6.5