1969

6.4

2011

5.8

2014

5.4

1997

7.6

1940

7.1

2010

7.0

2012

6.4

2007

5.8

2009

6.1

2015

5.4

2016

5.2

2000

7.6

2012

7.2

2003

7.8

2008

6.7

2017

7.3

2008

6.7

1998

7.3

1998

7.5

1980

8.2