1997

6.5

1999

5.6

1998

7.1

2009

6.8

2004

7.5

2000

6.8

1968

0.0

1984

6.8

2005

6.3

1988

6.6

2005

5.4

2006

5.5

2006

6.2

1997

6.6

1933

0.0

2015

8.0

2003

7.4

2001

6.8

1974

7.8

1991

8.3