1991

5.9

1997

6.2

1999

5.0

1990

6.3

2009

6.1

1972

7.7

2008

4.7

1996

7.1

2009

7.7

2000

7.1

2006

6.6

1989

7.0

2003

7.3

2007

5.7

2011

5.9

2005

5.2

2001

6.7

2012

7.0

2012

5.3

1999

7.4