1995

6.3

2013

6.3

2010

6.4

2011

6.1

1968

8.1

1982

7.5

2007

7.8

1997

7.9

2008

8.5

2016

5.9

1978

7.4

2014

8.0

2015

7.6

2004

6.5

2012

7.4

1990

6.9

1983

7.1

2007

7.0

2012

5.6

2017

6.3