2000

0.0

1970

5.5

1994

7.0

1990

7.7

1998

7.9

1985

6.5

2004

7.6

1996

7.4

1981

8.0

1984

7.3

1998

7.1

1992

7.5

1995

6.5

1998

7.4

1960

7.6

2002

6.8

1999

6.2

2005

7.2

1987

7.0

2007

6.8