A common maritime adventure
Choose which crate is sacrificed and watch general average spread one deliberate maritime loss across ship and cargo in exact proportion. Then test the working-paper model: lying can improve a selected expected gamble, while maxmin preferences make truthful reporting uniquely optimal.
A storm needs one sacrifice. The master acts for the common safety. The rule does something stranger than compensation: it turns the unlucky owner's physical loss into the same fractional loss borne by every interest that came home.
Lege Rhodia cavetur, ut si levandae navis gratia iactus mercium factus est, omnium contributione sarciatur quod pro omnibus datum est. Preserved in Digest 14.2.1, promulgated in 533; traditionally ascribed to the pseudonymous Sententiae attributed to Paulus. No surviving archaic Rhodian statute can be dated from this line.
The storm demands a fixed dollar amount of cargo. That fixed amount matters: equalizing who bears the same sacrifice is the true claim. Jettisoning two whole lots of different values would create two different total losses.
Manifest 14.2
Ship plus four cargo interests
Click a crate to sacrifice it
Your tea bears the sacrifice. The adjustment is being prepared.
Checking the invariant.
| Interest | Value | Physical loss | Made good | Contribution | Net loss | Loss / value |
|---|
Computing from the manifest.
Digest 14.2.1 supplies the Latin sentence in a compilation promulgated in 533.
CMI adopted the York-Antwerp Rules 2016 in May 2016. Rule A defines the act, Rule G fixes valuation time and place, and Rule XVII supplies the contributory-value arithmetic used here.
The Ever Given dates and public claim figures below come from the owner notice and contemporary reporting.
The browser recomputes CV = post-casualty value + allowance, r = L / CV, every contribution, every recovery, and every net-loss fraction.
Machine residual: computing.
The sacrifice amount is fixed and no lot loses more than that amount. Values are reader choices, not observed cargo values.
Freight, deductibles, interest, salvage apportionment, damage, charges, currency and contractual variations are omitted. This is the complete arithmetic only for this stripped manifest.
Balancing contributions against the allowance.
Independent reproduction: node research/general-average/verify-general-average.mjs. The verifier also runs seeded randomized manifests and the declaration game below.
The old text and the modern rules are not the same instrument, and the Digest does not prove an 800 BC statute. What survives is the architecture: a deliberate common-safety loss is made good by common contribution.
Digest 14.2.1 | 533 AD
“The Rhodian law provides that if cargo has been jettisoned in order to lighten a ship, the sacrifice for the common good must be made good by common contribution.”
Translation after Alan Watson. Jean-Jacques Aubert's historical correction is essential: this is a sixth-century compilation attributing a rule to Rhodes, not a surviving archaic Rhodian code.
York-Antwerp Rules | May 2016
“There is a general average act when, and only when, any extraordinary sacrifice or expenditure is intentionally and reasonably made or incurred for the common safety for the purpose of preserving from peril the property involved in a common maritime adventure.”
Computing the interval.
CMI Rule A. These private rules are commonly incorporated into carriage contracts; they are not an international treaty.
Ever Given is a different species of the same Rule A. No container jettison is claimed here. Its general average concerned extraordinary expenditure after grounding and refloating, not the toy sacrifice above.
Loading the verified timeline.
The first instrument assumed values were known. Anderlini and Teitelbaum ask what happens when the values are private and owners report them. Their 2024 working paper finds no truthful expected-utility equilibrium with truthful ordering in its general game, but truthful declaration is the unique Nash equilibrium for maxmin owners.
The other four declarations match whichever report you choose, and four of five boxes are lost. This is the paper's exact worst-case construction, not a forecast of a voyage.
Selected declaration: computing. Worst-case loss share among declared values: computing.
| Declaration | If sacrificed | If spared | Row minimum | Expected at selected belief |
|---|
Computing the row minima.
Computing the two-branch expected wealth.
The temptation is visible. A low report cuts every contribution. If your crate is spared, that can improve this two-branch expected gamble. If it is sacrificed, recovery is based on the low report and the floor drops. The maxmin owner compares the row minima, not an assumed probability, and honesty is the unique peak.
This instrument reproduces the working paper's worst-case algebra. It does not describe every actual adjustment. York-Antwerp Rule XIX(b) says wrongfully undervalued goods are allowed on the declared value but contribute on actual value. The paper explicitly studies the harder case of subjective private values where that corrective can be inoperable.
Computing the interval from Digest to working paper.