the portoria, customs and tolls on imports and exports, including among provinces. Special taxes were levied on the slave trade. Towards the end of his reign, Augustus instituted a 4% tax on the sale of slaves, which Nero shifted from the purchaser to the dealers, who responded by raising their prices. An owner who manumitted a slave paid a "freedom tax", calculated at 5% of value. An inheritance tax of 5% was assessed when Roman citizens above a certain net worth left property to anyone but members of their immediate family. Revenues from the estate tax and from a 1% sales tax on auctions went towards the veterans' pension fund (aerarium militare). Low taxes helped the Roman aristocracy increase their wealth, which equalled or exceeded the revenues of the central government. An emperor sometimes replenished his treasury by confiscating the estates of the "super-rich", but in the later period, the resistance of the wealthy to paying taxes was one of the factors contributing to the collapse of the Empire. Economy Scholar Moses Finley was the chief proponent of the primitivist view that the Roman economy was "underdeveloped and underachieving," characterized by subsistence agriculture; urban centres that consumed more than they produced in terms of trade and industry; low-status artisans; slowly developing technology; and a "lack of economic rationality." Current views are more complex. Territorial conquests permitted a large-scale reorganization of land use that resulted in agricultural surplus and specialization, particularly in north Africa. Some cities were known for particular industries or commercial activities, and the scale of building in urban areas indicates a significant construction industry. Papyri preserve complex accounting methods that suggest elements of economic rationalism, and the Empire was highly monetized. Although the means of communication and transport were limited in antiquity, transportation in the 1st and 2nd centuries expanded greatly, and trade routes connected regional economies. The supply contracts for the army, which pervaded every part of the Empire, drew on local suppliers near the base (castrum), throughout the province, and across provincial borders. The Empire is perhaps best thought of as a network of regional economies, based on a form of "political capitalism" in which the state monitored and regulated commerce to assure its own revenues. Economic growth, though not comparable to modern economies, was greater than that of most other societies prior to industrialization. Socially, economic dynamism opened up one of the avenues of social