1989

7.4

2007

6.1

2015

5.4

2000

6.8

1983

7.1

1981

6.6

1996

3.7

1994

6.1

2005

6.7

1955

7.1

1985

6.7

1985

6.5

2002

4.8

2008

6.5

2003

7.4

1980

6.6

1968

7.3

1970

7.1

1979

7.0

2001

6.8