1991

6.8

1988

6.1

1986

6.6

2007

5.3

1983

6.2

1986

6.3

1973

6.5

1996

5.9

2001

5.8

2003

6.1

1986

5.6

1969

7.8

1973

3.1

2007

6.3

1990

6.4

1994

5.2

1993

6.7

1985

6.1

2002

6.2

2007

7.9