1975

8.0

1997

7.1

2005

6.5

2006

5.6

2006

6.2

1998

6.1

2014

7.3

2007

5.8

2004

6.3

2003

4.2

1992

6.6

2000

6.5

2000

6.0

2002

6.4

1979

6.3

1981

6.1

1998

4.6

2000

6.1

2004

6.4

2003

6.5