1976

6.6

2000

6.0

2008

6.8

1988

7.4

1999

5.3

1980

6.7

2000

6.4

1990

6.1

2003

7.2

1999

6.6

2000

6.9

2004

7.3

1990

6.0

1993

7.3

1993

6.5

1991

6.2

1988

6.2

1984

6.1

1994

5.2

1996

5.4