2001

7.3

1996

6.4

1988

6.3

2005

5.3

2003

5.9

1997

6.0

2007

4.8

1992

7.4

1986

6.1

2007

4.0

2017

6.9

1970

7.1

2005

6.4

1964

7.1

2014

6.7

2009

6.6

1994

7.5

1980

6.6

2007

3.0

2016

0.0