1996

7.2

2002

6.7

1994

7.0

1983

6.2

1987

6.8

1975

7.2

1981

6.5

1981

6.7

2006

7.2

2003

6.1

2003

5.1

1987

6.0

2007

6.3

2002

6.2

1997

6.6

2008

6.0

1960

7.6

1992

6.0

2004

4.0

2005

5.7