1980

6.5

2015

5.4

1986

5.9

2002

6.2

2000

4.7

1988

6.7

2003

6.0

1998

7.5

2000

6.8

1996

5.7

1994

7.1

2004

6.9

1967

5.2

1985

7.6

2005

5.8

2002

6.1

2005

6.2

2007

6.2

1999

5.7

2002

5.7