1990

6.2

1991

6.8

1992

6.2

1971

7.2

1993

6.3

2008

6.6

1999

6.8

1994

5.8

1997

6.8

1997

6.9

1998

6.1

1978

7.5

1978

7.6

2000

6.1

2002

7.2

1971

7.4

2007

6.2

1994

8.5

1971

6.4

1987

7.5