1989

6.8

1993

7.0

1994

5.1

1991

7.1

2005

5.7

1985

7.2

2005

6.1

2006

6.2

2004

5.5

1978

7.4

1996

4.9

2007

6.0

1939

6.0

2002

4.8

1994

6.0

1992

5.3

2005

6.8

2007

6.1

1987

7.3

2008

4.8