1995

6.2

2005

6.2

1988

6.8

1996

6.4

1992

5.3

1987

7.0

1987

6.9

2006

7.1

1997

6.2

2002

6.0

2006

5.7

2001

5.8

1990

6.4

1977

8.8

1985

6.3

1970

6.9

2006

5.5

1997

6.5

1945

6.9

2004

6.1