1980

6.7

1990

6.1

1976

7.5

2009

5.6

2014

5.3

2007

7.2

1966

6.3

2006

7.0

1960

7.5

2009

8.5

1983

5.5

2004

6.5

1982

6.2

2020

5.5

1999

5.1

2008

6.9

1980

6.6

1996

6.7

1972

6.6

2016

6.7