2005

6.8

1999

5.4

2006

7.0

1984

6.0

1978

5.9

2007

6.4

2007

6.7

1996

5.6

2003

6.1

1975

5.7

1968

6.3

2003

6.1

2007

7.3

2007

6.3

1972

5.0

1992

5.7

2004

6.9

1965

6.3

1974

5.9

2001

1.3