1990

6.1

2000

5.5

2006

6.9

2010

6.1

1983

6.5

2002

5.2

1976

7.5

1987

5.3

2004

5.7

2007

6.7

1982

7.4

2012

6.4

2008

5.1

1999

5.1

2006

7.0

1988

7.5

2011

5.2

1961

7.7

1994

5.3

1980

6.2