provincial law conflicted with Roman law or custom, Roman courts heard appeals, and the emperor held final authority to render a decision. In the West, law had been administered on a highly localized or tribal basis, and private property rights may have been a novelty of the Roman era, particularly among Celtic peoples. Roman law facilitated the acquisition of wealth by a pro-Roman elite who found their new privileges as citizens to be advantageous. The extension of universal citizenship to all free inhabitants of the Empire in 212 required the uniform application of Roman law, replacing the local law codes that had applied to non-citizens. Diocletian's efforts to stabilize the Empire after the Crisis of the Third Century included two major compilations of law in four years, the Codex Gregorianus and the Codex Hermogenianus, to guide provincial administrators in setting consistent legal standards. The pervasive exercise of Roman law throughout Western Europe led to its enormous influence on the Western legal tradition, reflected by the continued use of Latin legal terminology in modern law. Taxation Taxation under the Empire amounted to about 5% of the Empire's gross product. The typical tax rate paid by individuals ranged from 2 to 5%. The tax code was "bewildering" in its complicated system of direct and indirect taxes, some paid in cash and some in kind. Taxes might be specific to a province, or kinds of properties such as fisheries or salt evaporation ponds; they might be in effect for a limited time. Tax collection was justified by the need to maintain the military, and taxpayers sometimes got a refund if the army captured a surplus of booty. In-kind taxes were accepted from less-monetized areas, particularly those who could supply grain or goods to army camps. The primary source of direct tax revenue was individuals, who paid a poll tax and a tax on their land, construed as a tax on its produce or productive capacity. Supplemental forms could be filed by those eligible for certain exemptions; for example, Egyptian farmers could register fields as fallow and tax-exempt depending on flood patterns of the Nile. Tax obligations were determined by the census, which required each head of household to appear before the presiding official and provide a headcount of his household, as well as an accounting of property he owned that was suitable for agriculture or habitation. A major source of indirect-tax revenue was