As time went on, relations between the settlers and the Jesuits soured. The native population of the Guaraní Indians, initially large compared to the number of Spanish settlers, decreased greatly. In part this was due to the abuse and overwork engendered by the encomienda system, a legal framework similar to slavery, and in part due to the Spanish laws that declared the offspring of Spaniards and their Guaraní wives to be Spaniards themselves and thus entitled to their own native slaves under encomienda. As immigration slowed, the province became heavily populated by Spanish-Guaraní mestizo (mixed blood) descendants, who, due to the increasing unavailability of pure-blood Guarani to claim as servants, became a new class of "poor whites." Meanwhile, the Guaraní on the Jesuit missions were flourishing, and many Guaraní actively chose mission life over remaining independent or risking falling into the encomienda system. The result was a perceived "shortage" of cheap encomienda labor - a shortage that could be fixed if the Jesuit mission Indians were taken and impressed into the encomienda. Additionally, the Jesuit missions were an economic competitor to Paraguay's settlers, as both's major export was yerba mate used for the production of the caffeinated drink mate. The variety of yerba produced in the mission lands (yerba caaminí) was considered superior to the yerba harvested in the civil province (yerba de palos), pushing down the Paraguayan's margins even further. Since the mission lands were closed off to almost all Paraguayans, wild rumors about Jesuit activities within them found easy currency among the Paraguayans. Tales of hidden great treasures and secret lucrative mines worked by captive Indians were not uncommon.