1970

7.2

1964

7.1

2009

6.6

2003

5.9

2017

6.9

2007

3.3

2003

5.4

1988

6.3

1997

5.9

2002

6.8

2002

6.4

2001

7.3

1996

6.4

2007

5.0

1980

6.6

1994

7.5

2014

6.7

1992

5.0

2010

3.9

2008

6.8