1997

6.2

2005

5.7

1999

5.8

1995

7.1

1980

7.1

2004

3.9

1994

6.1

1991

6.3

2006

6.3

2003

6.8

1977

6.2

2005

6.7

2006

7.4

2005

7.2

1997

7.0

1966

7.2

2008

2.0

1995

6.5

1983

6.6

1976

4.2