1983

6.5

1997

7.9

2000

8.0

2006

5.8

1984

6.7

1995

7.3

2005

6.6

2014

1.0

1972

6.9

2005

6.6

2025

0.0

1989

7.9

1990

6.1

1992

7.4

1994

6.6

1994

7.6

1961

8.1

2013

6.2

1940

5.0

1979

7.6