1995

7.3

1990

7.0

2007

5.8

1988

6.2

1985

6.6

1980

6.6

1968

7.2

1988

6.3

1994

5.8

2005

6.5

2000

6.4

2006

5.4

1974

6.1

1996

6.1

1992

5.0

2002

5.8

1985

6.0

1997

6.2

1984

5.5

2003

6.3