Pope John XXIII
Mater et Magistra §190
Mater et Magistra: On Christianity and Social Progress
190 As for the problems which face the poorer nations in various parts of the world, We realize, of course, that these are very real. They are caused, more often than not, by a deficient economic and social organization, which does not offer living conditions proportionate to the increase in population. They are caused, also, by the lack of effective solidarity among such peoples.
Source: Mater et Magistra (Vatican.va)