1990

6.2

2008

6.6

1996

6.9

1987

7.5

1952

6.9

2005

7.3

1999

7.2

1992

7.5

1984

7.2

1960

7.7

2004

7.6

1960

6.7

2006

7.9

2007

7.4

1999

6.8

2006

6.9

1991

6.2

1990

6.7

1993

5.5

1998

6.8