1997

8.4

2012

6.8

2007

8.5

2005

8.2

2005

8.7

2006

7.9

1996

7.7

1986

8.3

2015

8.3

2018

6.7

2016

8.6

2011

7.0

2007

6.0

2013

8.0

2023

5.9

2001

6.9

1970

8.7

2017

5.9