Why did Romans use the sesterce in written monetary records when the coin itself was so rarely used?

Question

In the vast majority of cases, Roman writers and government officials recorded amounts of money (money donated, value of items bought/sold, amount given in wills, etc.) in sesterces. Given that the sesterce was such a rarely-minted and rarely-used coin, why did the Romans choose to use that denomination for virtually all monetary records?**

*Admittedly, this is largely based on personal research: I have never seen a single mention of a sesterce coin found in Pompeii, Herculaneum, or a Roman British hoard, nor mention of the sesterce on a menu or graffiti. I'm sure there must have been some, but I've never come across it even once. The coinage in use in all those locations seemed to be the aureus, denarius, and as exclusively, despite widespread contemporaneous use of sesterces in records.

Answer 1

While in this case plenty of sesterces were actually coined, in general you might ask why the Carolingian Empire (and most of Europe for several more centuries) used librae in its accounts or why tribute to Athens was stated in talents, neither of which was ever coined. Uncoined units of account are a convenience that avoids the need of coins for monetary transactions and that cannot readily be debased. See David Graeber's Debt: The First 5000 Years for an extensive discussion. Units of account that do not correspond to coins are a normal feature of human civilizations, not something requiring a special explanation.

Also of interest if not directly relevant, since the sesterce was a quarter of a denarius, and a farthing is a quarter of the old penny (which was a denarius), a sesterce is literally a farthing. Since Roman soldiers around 1AD were paid about 900 sesterces a year, that translates to 18s9d, or about $1 a year. That gives you a vague sense of inflation over the last 2000 years. In the US Army a private first class with 10 years experience makes about $27000 per year. On the other hand, you can buy a lot more with $27000 today than with 900 sesterces back then. For purchasing military labor prices may have gone up 25000x, but for many goods it's more like 500x (with a wide range, obviously).

Answer 2

The penny or cent remains a unit of account despite being eliminated in Canada and approaching uselessness in other Western Nations such as the U.S. and U.K.

For financial transactions the basis point, a mere 1/100th of a cent, remains the most common unit in which prices and interest rates are denominated.

Basis points (BPS) refers to a common unit of measure for interest rates and other percentages in finance. One basis point is equal to 1/100th of 1%, or 0.01%, or 0.0001, and is used to denote the percentage change in a financial instrument.

Using a unit of account significantly smaller than one's currency eases the maintenance of precision in large transactions without recourse to fractions. This was particularly important in ancient financial systems with the understanding of fractions being both weaker and much less widespread than today.