1987

6.7

2001

6.0

1982

7.2

1993

7.0

1998

7.3

2007

6.7

2007

6.7

1992

6.7

1993

6.1

2002

5.9

1997

6.4

1977

6.2

2008

4.9

2003

7.1

2006

6.1

1999

5.7

2009

6.0

1991

6.3

2006

5.0

2005

5.1