1997

6.1

2015

5.3

2011

6.5

1980

6.6

1995

5.6

2009

7.3

2005

6.9

1971

6.8

1965

6.8

2016

6.1

2009

7.1

2014

5.8

2020

6.5

2016

6.8

5.3

2003

6.3

1999

5.9

2006

6.8

2015

6.5