1990

6.2

2002

4.3

1985

5.9

2002

5.8

2009

4.2

1996

6.9

2008

5.9

2009

5.7

1962

7.4

2009

4.8

2009

5.9

2007

5.6

2003

5.4

2001

6.0

1989

6.7

1947

6.9

1975

6.0

1986

5.4