McLaughlin discusses the importance of the tetarte – a 25% tax on imported goods coming into the Empire via the Indian Ocean trade (and other routes) – for the functioning of the Roman state’s finances. He suggests that around one-third of the total state revenues were generated by taxation on eastern imports both directly (via the tetarte), through an intra-territorial trade of these imports (that is through portoria, internal customs dues within the Empire), as well as through taxation on goods that were exported to the East in exchange for these commodities.