2004

4.7

2011

4.9

2007

4.9

2006

4.1

2012

5.1

1998

6.6

1978

6.9

1999

6.1

2011

2.8

2005

6.2

2013

7.4

1994

7.9

2005

5.0

2014

6.8

2016

7.9

2009

7.2

2011

7.3

1990

7.7

2010

6.6

2017

8.1