1988

7.7

2000

7.6

2001

5.3

2003

7.6

1980

5.8

2000

8.0

1973

6.6

2005

6.0

1974

5.2

1996

7.8

2006

8.1

1996

7.5

1972

6.5

1996

7.3

1994

0.0

2008

7.6

2005

8.0

2009

5.0

1986

7.2

2010

7.9