2016

4.2

1983

4.0

2015

6.3

2014

7.1

1991

6.1

1999

6.6

2007

1.0

1978

3.8

1977

0.0

2002

6.5

1981

5.5

1986

5.0

1990

5.8

2005

0.0

2004

6.3