1997

7.1

2015

6.5

2018

6.3

1981

7.5

2012

5.3

2000

7.2

2006

6.1

1968

5.8

1989

9.5

2005

8.8

1978

6.8

2003

8.5

1993

6.5

1973

8.0

1998

7.9

2004

7.6

2002

7.0

1992

6.5

1973

5.7

2000

6.2