1974

4.8

1990

4.6

1997

5.1

1982

4.9

1983

4.1

1973

4.6

2003

4.8

1970

4.8

1981

5.7

1968

3.8

2002

3.8

1974

3.9

1976

4.2

2015

3.5

2011

4.4

2013

3.5

2005

3.2

1996

1.8

2008

4.5

2010

0.0