1990

7.8

2010

7.9

1994

6.7

2000

5.4

2008

6.5

2002

6.4

2021

7.2

1995

8.0

1999

7.6

2017

6.3

2001

7.1

2001

7.9

2004

8.0

1995

7.2

2006

7.0

2005

6.9

1960

7.5

1952

7.4

2014

8.5