1981

6.4

1995

6.0

1986

6.9

1988

6.2

1998

6.1

2006

5.0

1979

7.0

1984

6.9

1994

4.9

1957

4.2

1979

6.1

1985

6.6

1999

8.0

2000

5.4

2001

7.1

1986

8.0

2005

6.5

1987

7.5

2013

6.5

1997

3.5