1985

5.3

1997

7.3

2001

6.0

2005

7.1

2003

5.4

2009

6.1

2006

5.5

2007

6.1

2006

5.9

1999

5.8

2003

5.8

2006

5.2

1990

6.4

1999

6.8

1987

5.3

2002

5.9

1998

6.5

2005

7.5

1973

6.9

1991

3.7