1980

8.2

2006

8.2

2004

7.2

2007

6.8

1981

6.7

1991

9.0

1999

7.5

1990

7.5

1993

6.2

1968

4.7

2018

6.1

2017

7.2

2001

7.4

1975

6.7

1997

6.6

1960

7.4

2004

6.2

1993

7.5

1964

6.8

1997

5.9