2005

6.8

1997

6.8

1995

6.5

2006

7.0

1984

6.0

2003

6.8

2005

7.3

1992

5.2

2003

6.1

2007

7.5

2008

6.2

2003

5.8

2002

7.3

2006

5.7

2002

6.3

2007

6.7

2004

6.6

1969

6.0

1981

6.2

1975

6.6