1998

8.2

2009

5.9

1996

5.6

1997

7.5

1999

6.5

1997

6.6

1990

5.8

2007

6.4

2008

6.5

1996

6.0

2004

7.2

1988

7.1

1985

4.4

1982

5.3

2005

5.6

1999

6.7

1960

7.4

1987

6.8

1981

6.5

1975

6.5