1982

6.1

1997

6.4

2003

5.1

1975

6.8

2008

6.1

1980

6.3

1977

6.8

1976

5.6

1972

6.3

1996

6.8

2004

5.9

2002

6.4

2006

6.2

1987

6.8

1989

5.8

1987

7.1

2009

7.6

2000

7.0

1981

6.4

2017

4.0