1975

5.8

2009

5.6

2018

5.9

7.8

2007

6.0

1998

6.2

2011

5.5

2014

6.7

2020

5.5

2002

7.4

1977

6.5

1981

7.2

2015

5.7

2016

5.3

2009

8.5

2010

6.7

2017

5.9

2010

5.2

2011

7.4