1983

7.9

1995

4.6

2011

7.3

1991

6.2

2007

5.9

1997

5.4

2013

5.9

1994

6.2

2008

7.5

2003

5.9

2017

7.2

1985

6.7

1942

7.0

1982

5.2

2011

5.9

1964

7.3

2011

6.5

1999

6.2

2013

6.1

2016

6.8