1965

6.8

2000

7.2

1983

7.9

1965

6.7

2007

6.1

1971

6.8

2002

8.4

1981

6.9

1988

7.3

1995

5.7

2010

6.6

1991

7.2

2015

4.6

2008

7.0

2011

5.5

1967

6.5

2007

6.0

1974

7.0

2012

6.1

2003

5.8