1970

5.6

2006

6.0

2005

6.5

2003

7.2

1999

6.6

2000

6.9

2007

7.2

1998

7.5

2007

6.5

1992

6.6

1983

7.4

1991

6.6

1995

7.3

2002

6.6

2016

6.1

1988

5.0

1997

6.3

1984

6.8

1994

6.7

1992

7.4