1989

8.0

1999

8.7

2011

8.5

2011

7.6

2010

8.1

2013

7.5

2007

7.7

2006

8.2

2004

8.1

2011

7.6

2004

8.6

2008

8.4

2012

6.4

2011

8.1

2012

6.8

2011

8.1

2002

8.1

2012

7.6

2009

6.8

2009

8.0