1975

6.8

1984

5.7

2006

5.6

2017

4.5

1995

8.2

2008

8.5

1997

7.4

2003

5.8

1994

8.3

1976

8.1

2003

8.3

1974

7.9

2001

7.8

1999

7.0

2008

6.6

2004

7.2

1990

6.8

2008

5.7

2005

6.5

2008

7.5