1990

6.1

1996

5.8

1988

6.1

1975

6.4

1993

5.8

1976

7.5

1952

6.7

1998

6.0

1982

7.4

1983

6.5

2009

6.2

2010

7.8

2001

6.4

1989

5.5

1997

7.9

2017

4.5

1999

5.1

1999

6.2

2006

5.5

1986

7.6