2001

4.7

2005

4.3

1989

3.7

1973

6.6

1968

4.8

2008

5.6

1995

4.9

1987

5.3

1976

4.8

2002

4.8

1997

5.1

2002

6.0

2007

6.1

1984

2.5

1991

5.4

2006

5.0

1970

3.3

1970

4.1

1989

3.6

1997

2.4