1992

6.3

2002

6.7

1982

6.1

1970

5.3

1997

6.4

1975

6.8

2002

6.5

2017

8.5

2007

4.5

2008

5.0

1976

5.6

1996

6.8

1972

6.9

2004

5.9

1943

7.5

2004

6.7

1998

7.2

2009

7.3

1981

7.3

2009

7.6