1972

7.1

2007

6.4

1988

7.8

1997

7.1

2005

6.4

2001

7.4

1995

6.6

1975

7.7

1987

4.1

2006

6.7

1986

2.7

2001

3.3

2005

7.1

1971

7.2

1993

6.3

1999

7.1

1981

7.1

1999

7.2

2007

6.2

2008

6.6