2005

6.8

1995

6.2

1970

6.8

1991

6.7

1992

6.0

2002

6.2

1993

7.2

1993

6.8

1992

5.4

1985

7.1

2005

6.7

1959

6.8

1980

6.2

1964

6.8

2005

6.2

1997

6.2

2004

7.1

2000

5.9

2006

5.1

2007

6.8