1994

8.5

2004

7.5

1975

7.8

1990

7.4

1992

6.8

1986

7.6

1995

8.4

2001

7.8

1980

7.3

1997

6.6

1999

6.3

2002

6.0

1974

7.9

1951

7.7

1983

7.2

1988

7.5

1952

8.1

2014

7.0

2017

4.7

2008

8.5