1995

7.5

1999

8.4

2008

6.3

1980

8.1

1985

7.7

1986

7.2

2007

5.9

2010

7.5

2009

6.7

2011

8.3

1998

8.1

1992

6.9

1969

7.1

1960

7.6

2012

6.9

1999

6.2

2014

7.8

2005

6.2

2009

6.4

2007

7.2