One of the most important aspects of the recent mass migrations of Latin Americans into previously remote regions of the hemisphere is the impact these have had on areas cut by international boundaries. With the exception of the United States-Mexico border, however, historical examination of the process is still in its infancy. And few observers have developed a satisfactory theoretical basis explaining an admittedly complex process.One exception was Cuban historian Jorge Mañach, who spoke of “balanced” and “unbalanced” frontiers, largely in the context of the United States-Mexican boundary. He believed that power distribution between nations determined the degree to which their frontier interrelationships were equal or unequal. In Mañach's view, when a politically or economically weaker nation shares a boundary with one that is stronger, overall communication is sacrificed and the stronger power inevitably “spills over” into the neighboring region, economically and culturally.