1983

7.9

2013

6.8

2007

6.9

2009

7.0

1996

7.1

1997

6.5

2010

6.0

2002

6.6

2014

5.6

2006

5.7

2015

5.8

2012

6.1

1976

7.5

2011

6.3

2003

6.5

2010

5.8

2013

7.6

2004

6.2

2013

6.3

2014

6.2