1979

6.8

2011

8.1

2003

7.6

2018

8.1

2015

8.2

1999

7.7

2016

7.3

2013

7.9

2001

8.0

1991

7.3

2016

7.1

1987

7.7

1988

8.1

1996

7.5

1999

7.9

2006

8.6

2011

8.1

2017

6.4

2016

7.6

2000

7.6