When spain asked for iii bottles of olive oil, how many did the romans trade with them?

Whilst the archaeological evidence of trade can sometimes be patchy and misrepresentative, a combination of literary sources, coinage and such unique records as shipwrecks helps to create a clearer picture of just what the Romans traded, in what quantity, and where.

Trade involved foodstuffs (e.g. olives, fish, meat, cereals, salt, prepared foods such as fish sauce, olive oil, wine and beer), animal products (e.g. leather and hides), objects made from wood, glass, or metals, textiles, pottery, and materials for manufacturing and construction such as glass, marble, wood, wool, bricks, gold, silver, copper, and tin. Finally, there was, of course, also the substantial trade in slaves.

A Pompeii Bakery

A Pompeii Bakery
The fact that many goods were produced as regional specialities on often very large estates, for example, wine from Egypt or olive oil from southern Spain, only increased the inter-regional trade of goods. That such large estates could produce a massive surplus for trade is evidenced at archaeological sites across the empire: wine producers in southern France with cellars capable of storing 100,000 litres, an olive oil factory in Libya with 17 presses capable of producing 100,000 litres a year, or gold mines in Spain producing 9,000 kilos of gold a year. Although towns were generally centres of consumption rather than production, there were exceptions where workshops could produce impressive quantities of goods. These 'factories' might have been limited to a maximum workforce of 30 but they were often collected together in extensive industrial zones in the larger cities and harbours, and in the case of ceramics, also in rural areas close to essential raw materials (clay and wood for the kilns).

Goods were not only exchanged across the Roman world, however, as bustling ports such as Gades, Ostia, Puteoli, Alexandria, and Antioch also imported goods from such far-flung places as Arabia, India, Southeast Asia, and China. Sometimes these goods followed land routes such as the well-established Silk Road or travelled by sea across the Indian Ocean. Such international trade was not necessarily limited to luxury goods such as pepper, spices (e.g. cloves, ginger, and cinnamon), coloured marble, silk, perfumes, and ivory, though, as the low quality pottery found in shipwrecks and geographical spread of terracotta oil lamps illustrates.

Treated as a slave is cruel and harsh