1997

7.1

1998

6.1

2007

6.4

1951

5.8

1986

6.9

1960

7.7

2004

7.0

2001

6.3

1977

6.3

2006

7.0

2001

6.4

2001

7.3

1999

6.8

2003

6.7

2016

6.1

1998

6.5

2008

7.0

2000

4.4

2002

7.4

2008

5.8