1970

7.1

1964

7.1

2005

6.4

2001

7.3

1992

7.4

2002

6.8

2003

5.9

1996

6.4

1988

6.3

2005

5.3

1986

6.1

1994

7.5

2007

4.8

2009

6.6

2014

6.7

2018

4.0

1996

5.3

2017

5.0

2010

3.9

2007

3.0