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B - 20 : Treasures on the Sea

Updated: Apr 5, 2021

Yesterday, we learned that the citizens of Rome consumed around 300’000 tons of wheat per year and needed the equivalent of 500 Carpe Diem V to ship this cargo from Egypt and Sicily to Ostia, the capital’s main port.

Carpe Diem V - our home this summer!

The above number does not include the 250’000 Roman Legionnaires which formed the Roman Army. These guys consumed about twice as much as an ordinary citizen which adds another 150’000 tons to the bill (not counting the oats for their horses).

English guys reenacting Roman Legionnaires -

their replica gear is exactly as it was

We are now at a total of 450’000 tons a year and the number of grain ships has just gone up fro 500 to 750. Since many of us are in Business or in Finance, you may wonder how much this trade was worth.

Accurate data on prices in Roman times are peevishly difficult to obtain and the sources often contradict each other. But I will give it a try anyway since I found some more or less consistent data for the price of a loaf of bread at the time when Pompeii succumbed to the ashes of Vesuv (79 AD).

Bronze Modius, basic measurement cup for wheat -

1 Modius = 6.7kg of wheat


Let me walk you thru the equations I use:

- with 1 Modius of wheat (6.7kg) one could bake 16 - 20 loafs of bread (one pound)

- two loaves of bread cost around 1/8 of a Denarius (discounting the cost of labor which was performed by slaves)

- one Modius of wheat was thus worth close to one Denarius (or 3.25 g of pure silver)

- 450’000 tons of wheat (divided by 6.7 kg) are then worth 67.2 millions Denarii or 218.3 tons of silver

- at today’s silver prices of USD 514.- per kg, this would represent a total of USD 112.2 millions

- in antiquity, the exchange rate between gold and silver was at 1:10 much more favorable. Today - due to much improved mining & refining techniques - it dropped to 1:75

- using the old exchange ratio of 1:10 and valuing gold at USD 40'000/kg, the value of 450’000 tons of wheat would jump to USD 873 million - a truly staggering number!

- at today's price levels, a metric ton of wheat costs about USD 210.- Thus, 450'000 tons would cost today USD 94.5 million - still a high number. Given the significant increase in agricultural productivity, the USD 873 million number may be not that wrong

Trajan's Denarius contained 3.25 g of silver

But maybe this is the wrong comparison and we should ask ourselve what we could have bought or hired at the time for 67.2 millions Denarii. Here is the answer - again to be taken with a big grain of salt. The entire wheat trade had an equivalent value p.a. of:


- 16.8 millions Tunicas (the main Roman cloth) @ 4. dinarii a piece (Rome had 50 - 60 million people)

- 537’600 donkeys @ 125 Denarii the animal

- 107’520 slaves (@ 625 Denarii on average) - there were about 5 million slaves in the Roman Empire

- 280’000 Roman Legionnaires for a full year - 240 Dinarii p.a. - the Roman Army counted “only” 250’000 Legionnaires!

- 18'666 Roman Centurions for a full year at 3'600 Dinarii p.a. each - the Roman Army had only 4'000 Centurions

Roman slaves serving refreshments - mosaic from Pompeii

We are really talking about truly astonishing sums - even considering the shaky precision of our sources. More tomorrow

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