1990

6.9

2000

7.2

2006

6.7

2000

6.5

1956

6.2

2004

6.1

1977

7.1

2006

7.1

2003

6.6

1998

6.5

1977

6.3

2004

6.9

2002

6.7

2004

6.8

2005

6.7

1972

6.9

1973

7.8

1980

6.2

2017

6.3

2002

6.0