1968

7.1

1994

5.8

1987

6.5

1977

5.3

2014

6.2

2010

7.2

2004

2.0

2013

5.3

1980

7.7

2006

6.6

2002

7.5

2004

7.3

1982

6.6

1985

7.6

2001

6.5

2003

6.6

2008

4.5

1981

6.7

2002

7.4

2007

6.6