1973

6.8

1990

5.9

2009

5.5

1985

8.1

2009

5.6

2007

4.9

2001

6.1

2012

7.2

1956

7.1

2009

7.1

2011

5.8

1989

6.1

1995

5.3

2009

5.0

2006

5.5

1937

7.0

1991

6.5

2010

7.4

2015

6.9

1997

6.0