1991

8.3

1996

7.9

2004

7.2

1965

6.4

2006

7.4

1999

7.0

2000

7.4

2005

6.5

1968

6.8

1987

6.0

1971

7.5

2003

7.4

1988

6.6

2005

5.5

2020

4.9

1990

6.1

2001

5.7

1993

6.6

2014

6.7

2005

6.5