In addition, the middle of the 18th century mining production intensified, putting more and more of a burden on the "mita," or draft labor, system. While Potosi's mining "mita" had already been dangerous and labor-intensive work as well as forcing a migration by both the native worker and sometimes their families to Potosi to work, the labor became more extractive during this time, even though no new veins of ore had been discovered. Indeed, many future rebellious areas centered around Potosi and the mining district.