1990

5.5

2011

5.9

1997

6.5

1992

5.3

1996

5.5

2005

6.2

2000

6.9

1994

7.9

1995

6.2

2004

6.2

1993

6.3

1975

6.1

1994

6.5

1994

6.8

2003

6.9

1987

6.9

1996

7.3

2003

5.1

1986

6.1

2001

5.6