The Roman Empire was overwhelmingly an agricultural economy: over 80% of the population lived and worked on the land. Therefore, rights over land use and product were the most important determinant of wealth. Roman conquest and rule probably led to a major downgrading of the economic position of the average "peregrinus" peasant, to the advantage of the Roman state, Roman landowners and loyal native elites. The Roman Empire was a society with enormous disparities in wealth, with the senatorial order owning a significant proportion of all land in the empire in the form of vast "latifundia" ("large estates"), often in several provinces e.g. Pliny the Younger's statement in one of his letters that at the time of Nero (r.54–68), half of all land in Africa proconsularis (Tunisia) was owned by just 6 private landlords. Indeed, the senatorial order, which was hereditary, was itself partly defined by wealth, as any outsider wishing to join it had to meet a very high property qualification (250,000 "denarii").