1980

4.7

1982

6.5

1999

6.0

2009

2.0

1997

6.1

1970

6.3

1969

5.6

1998

6.2

1987

4.9

2005

7.0

1998

6.0

2005

6.3

2003

5.9

1987

6.9

2005

5.0

2006

4.6

2008

5.2

2005

6.0

2006

5.3

2004

6.4