1987

6.5

1997

6.7

2006

6.1

1985

6.4

1992

5.3

1996

5.5

1980

6.9

1977

7.0

1983

6.2

2007

6.4

2005

5.4

1989

6.1

1996

5.9

2003

6.8

2003

5.9

1978

6.3

2003

5.0

1997

7.0

1997

4.5

2016

5.2