1987

6.9

2005

6.0

2001

7.0

2004

6.1

2006

5.6

1967

5.4

2006

6.8

1981

6.2

1982

5.9

1984

6.1

1985

5.3

2006

6.8

2016

5.8

2018

6.3

2018

7.5

1984

7.2

2006

7.1

2007

6.1

2014

3.1

2008

6.6