Sources

To see the source, simply click on the link and the source will open on a new page.

In Overview:

1: http://www.worldbank.org/ (see definition of International Poverty Line)

2: http://www.un.org/esa/socdev/unyin/documents/ydiDavidGordon

3: Map courtesy of www.theodora.com/maps used with permission

4: https://www.cia.gov/