1986

6.8

2006

6.2

2011

6.1

2006

6.1

2010

6.1

2010

5.8

1997

6.2

1994

6.2

2005

7.1

1992

7.4

1956

7.8

1991

8.1

2011

6.8

2004

7.3

2000

7.4

2008

7.8

2002

7.6

1989

7.2

2009

5.7

2013

6.8