Who is poor in the world? Much depends on how you measure it. But critics of measuring poverty do not get very far. This economist has resorted to a poem. It is a first for >i>Challenge>/i>, and we hope its cleverness conveys a message.

If the income of the poor falls or rises by the same percentage as it does for the rich, economists generally say that income inequality has not changed. But not all analysts believe this is true assessment of social and economic equity, especially in poorer countries. A 10 percent increase for...