36 KiB
36 KiB
OTIVM-IV Cost Calibration Model — Additional Goods, c. 14 BCE
Prepared for: OTIVM-IV / CIVICVS Simulator
Date: 2026-05-03
Status: Calibrated historical-economic model, not a claim of exact reconstruction
Previous document: otivm_iv_cost_calibration_model.md (ceramic cup baseline)
Currency: 1 dn = 16 as (unchanged)
Compatibility constants inherited from the ceramic baseline
AS_PER_DENARIUS = 16
WAGE_UNSKILLED_DAY_DN = 0.50
WAGE_SKILLED_ARTISAN_DN = 1.00
WAGE_MERCHANT_SELF_DN = 1.00
WHEAT_MODIUS_DN = 0.75
PORTORIA_AD_VALOREM_RATE = 0.025
CERAMIC_CUP_PLAIN_LOCAL_AS = 2.00
CERAMIC_CUP_FINE_LOCAL_AS = 4.00
Values below preserve the same method as the first document: source-backed anchors where possible, analogical conversions where evidence is adjacent, and explicit simulator calibration where the equation needs a value but the surviving evidence is not price-complete.
Good 1 — Garum
Garum is economically distinctive because it is coastal, specialist, salt-intensive, batch-produced, and quality-stratified: common fish sauce and luxury garum are not the same economic object. It stress-tests the model’s ability to handle fermentation time, container cost, perishability, and a very steep common/luxury multiplier. The main source challenge is that famous ancient testimony emphasizes elite-grade garum, while the game needs ordinary commercial amphora-scale product. Therefore the common product below is a calibrated market good anchored by fish-sauce archaeology, Pliny’s luxury-price testimony, later price schedules, and the ceramic-container baseline.
Baseline assumptions
- Product: standard commercial garum/liquamen, not
garum sociorumorflosgrade. - Production location: coastal officina in Roman Italy using local anchovies, sardines, mackerel, and trimmings.
- Sale context: wholesale to a negotiator or direct to a Roman urban market.
- Unit: one finished amphora, modeled as approximately 26 litres.
- Production mode: seasonal batch, with 2–3 months elapsed fermentation but limited active labour days.
Cost components
| Component | Amount (dn or as) | Source | Confidence | Notes |
|---|---|---|---|---|
| Raw fish, per amphora output | 1.25 dn = 20 as | Robert I. Curtis, Garum and Salsamenta (1991); Sally Grainger, The Story of Garum / fish-sauce reconstructions; general Roman fish-salting archaeology. | LOW | Direct Augustan Italian fish prices per amphora-equivalent are not preserved. Value assumes common small fish or trimmings, not premium table fish. |
| Salt | 0.75 dn = 12 as | Curtis, Garum and Salsamenta; Pliny, Natural History 31 on salt and fish sauces; modern work on salt as a fiscal and strategic commodity. | MEDIUM | Salt is essential and fiscally visible. Model treats salt burden as production input; no separate garum excise is modeled. |
| Fermentation overhead, 2–3 months | 0.80 dn = 12.8 as | Fish-salting workshop archaeology; Curtis; Andrew Wilson and Annalisa Marzano on Roman fish-processing installations. | LOW | Mostly space, vat occupation, monitoring, and capital lock-up. Fermentation time is long, but active labour is intermittent. |
| Amphora container | 1.00 dn = 16 as | Ceramic baseline document; J. Theodore Peña, Roman Pottery in the Archaeological Record (2007); amphora archaeology. | MEDIUM | Larger and more robust than the 2-as cup. This is a simulator-derived amphora constant, not a direct price. |
| Specialist labour, garum maker | 1.20 dn = 19.2 as | Baseline skilled wage WAGE_SKILLED_ARTISAN_DN = 1.00; Curtis; fish-sauce production reconstructions. |
LOW | Active work includes salting, packing, inspection, skimming, and transfer. Assumes batch labour amortized per amphora. |
| Workshop rent / coastal vat access | 0.60 dn = 9.6 as | Roman fish-processing officinae at coastal sites; Marzano, Harvesting the Sea (2013); Curtis. | LOW | Access to vats and coastal processing space is real but not priceable per amphora from direct evidence. |
| Portoria, if transported inland/inter-regionally | 0.30 dn = 4.8 as | Default PORTORIA_AD_VALOREM_RATE = 0.025; Roman portoria studies including S. J. De Laet and Peter Ørsted; previous ceramic baseline. |
MEDIUM | Calculated as 2.5% of 12 dn retail value. Use 0 if produced and sold locally inside the same toll district. |
| Spoilage / degraded batch allowance | 0.60 dn = 9.6 as | No direct source — simulator calibration; informed by perishable-food handling and amphora-loss logic. | LOW | Uses 8% loss burden on a production cost base near 7.5 dn. Increase in hot weather, poor sealing, or long storage. |
| Retail price, common garum amphora | 12.00 dn = 192 as | No direct source — simulator calibration; bounded against luxury garum testimony in Pliny and later fish-sauce prices in Diocletian’s Edict. | LOW | Standard commercial amphora. Chosen to sit far below garum sociorum while still being high-value relative to grain. |
Luxury comparator: garum sociorum amphora-equivalent |
600–1,000 dn | Pliny, Natural History 31.94; common scholarly note that elite Spanish garum could sell for roughly 1,000 HS for two congii. | MEDIUM | 1,000 HS = 250 dn for roughly 6.5 L; amphora-equivalent is extreme. Use only for luxury multiplier, not common trade. |
Specific findings
- Common vs luxury differential. The common amphora constant is 12 dn; the luxury amphora-equivalent implied by Pliny’s elite-grade testimony may exceed 600 dn and can plausibly reach about 1,000 dn. Simulator multiplier:
GARUM_LUXURY_MULTIPLIER = 64.0, with an allowed range of 50–100. - Tax treatment. Do not model a separate garum tax unless a route event requires it. Fiscal pressure is represented by salt input cost plus ordinary
portoriawhen the amphora crosses a toll boundary. - Shelf life. Properly sealed fish sauce is a stored fermented product, not fresh fish; risk is mainly seal failure, heat, leakage, adulteration, and quality degradation. Use spoilage as a batch-quality and transport-risk parameter, not as immediate decay.
Simulator constants
GARUM_UNIT_LITRES = 26.00
GARUM_RAW_FISH_DN = 1.25
GARUM_SALT_DN = 0.75
GARUM_FERMENTATION_OVERHEAD_DN = 0.80
GARUM_AMPHORA_DN = 1.00
GARUM_SPECIALIST_LABOUR_DN = 1.20
GARUM_WORKSHOP_ACCESS_DN = 0.60
GARUM_SPOILAGE_RATE = 0.08
GARUM_PORTORIA_RATE = 0.025
GARUM_COMMON_RETAIL_DN = 12.00
GARUM_COMMON_WHOLESALE_DN = 9.00
GARUM_LUXURY_MULTIPLIER = 64.00
GARUM_SHELF_LIFE_DAYS = 180
Recommended cost equation:
garum_common_cost_dn =
GARUM_RAW_FISH_DN
+ GARUM_SALT_DN
+ GARUM_FERMENTATION_OVERHEAD_DN
+ GARUM_AMPHORA_DN
+ GARUM_SPECIALIST_LABOUR_DN
+ GARUM_WORKSHOP_ACCESS_DN
+ (GARUM_COMMON_RETAIL_DN * GARUM_PORTORIA_RATE)
+ ((GARUM_RAW_FISH_DN + GARUM_SALT_DN + GARUM_FERMENTATION_OVERHEAD_DN
+ GARUM_AMPHORA_DN + GARUM_SPECIALIST_LABOUR_DN + GARUM_WORKSHOP_ACCESS_DN)
* GARUM_SPOILAGE_RATE)
= 6.02 dn before merchant acquisition margin
Confidence register
| Model value | Confidence | Reason |
|---|---|---|
| Garum as coastal specialist batch product | HIGH | Strong textual and archaeological support. |
| Salt as fiscal/strategic input | MEDIUM | Well-attested salt importance; per-amphora cost is inferred. |
| Common garum retail at 12 dn/amphora | LOW | Needed by model; no direct Augustan common-amphora price. |
| Luxury multiplier 50–100x | MEDIUM | Pliny anchors extreme elite price; conversion to common multiplier is analogical. |
| 8% spoilage / degradation | LOW | Practical calibration, not directly attested. |
| Amphora at 1 dn | MEDIUM | Compatible with ceramic baseline and amphora role; direct price not secure. |
Open questions / calibration flags
- Direct price evidence for common Italian garum remains weak; keep this product explicitly marked as calibration-heavy.
- If future route mechanics distinguish
liquamen,garum,muria, and luxurygarum sociorum, each should become a separate quality tier. - Salt tax should not be double-counted with
portoria. Use salt as production input and portoria as movement toll. - Garum is profitable only if the product is quality-controlled and sealed; add spoilage events for poor amphora quality, heat exposure, or delayed sale.
Good 2 — Grain (bulk, 100 modii)
Grain is economically distinctive because it is a staple bulk commodity with low margins, high volume, and strong state involvement. It stress-tests the model’s ability to handle scale, sea freight, horreum storage, spoilage, and margin compression under the shadow of the annona. The primary source challenge is that the best evidence concerns state supply, taxation-in-kind, crisis prices, and later freight schedules, not a clean private Augustan merchant ledger. The model therefore treats private grain trade as viable but constrained, with profit coming from volume and timing rather than high per-unit markup.
Baseline assumptions
- Product: common wheat (
triticum), not emmer or spelt. - Unit: 100 modii, a small merchant-legible consignment.
- Origin: North Africa or Sicily; North Africa used as default because of later centrality and strong evidence for Rome-facing grain flows.
- Destination: Ostia / Rome grain market.
- Scope: private merchant trade, not annona distribution, but with annona pressure constraining speculative margin.
Cost components
| Component | Amount (dn or as) | Source | Confidence | Notes |
|---|---|---|---|---|
| Purchase price at origin port, 100 modii | 50.00 dn | Rickman, The Corn Supply of Ancient Rome (1980); Erdkamp, The Grain Market in the Roman Empire (2005); baseline WHEAT_MODIUS_DN = 0.75. |
MEDIUM | Uses 0.50 dn/modius origin purchase, below Rome/Ostia destination price. Direct Augustan private origin price is not fixed. |
| Loading and porterage at origin | 2.00 dn | No direct source — simulator calibration; Roman dock labour analogized from wage anchors. | LOW | 4 unskilled day-wage equivalents for weighing, sacking/basket movement, and loading. |
| Sea freight / vectura | 8.00 dn | Rickman, The Corn Supply of Ancient Rome, using Diocletianic sea freight ratios as later evidence; Casson, Ships and Seamanship. | MEDIUM | Rickman notes sea freight could be a modest percentage of grain value and far cheaper than land carriage. Uses about 10.7% of destination value. |
| Portoria at destination | 1.875 dn | Default PORTORIA_AD_VALOREM_RATE = 0.025; portoria scholarship; prior model. |
MEDIUM | 2.5% of 75 dn destination wholesale value. If grain exemptions or annona contracts apply, set to 0. |
| Unloading and porterage at destination | 2.00 dn | No direct source — simulator calibration; dock labour analogized from wage anchors. | LOW | Symmetric with loading. Raise if bottlenecked at port or if inspected/seized. |
| Horreum rental / storage, one month | 1.50 dn | Rickman, Roman Granaries and Store Buildings; Ostia horrea archaeology; no secure Augustan rental tariff. | LOW | 0.015 dn/modius/month. Storage is real and archaeologically visible; price is calibrated. |
| Spoilage / loss in transit | 1.50 dn | Rickman on sampling, adulteration, and grain-control problems; no direct rate. | LOW | 2% value loss on 75 dn destination value. Includes damp, pests, adulteration, and handling loss. |
| Wholesale price at destination market | 75.00 dn | Baseline WHEAT_MODIUS_DN = 0.75; Rickman; Erdkamp. |
MEDIUM | 100 × 0.75 dn. This is the anchor inherited from the first document. |
| Net margin per 100 modii after costs | 8.125 dn | Derived. | MEDIUM | 75 - (50 + 2 + 8 + 1.875 + 2 + 1.5 + 1.5) = 8.125 dn, or 10.83% of revenue. |
Specific findings
- Origin-destination spread. The working spread is 0.50 dn/modius at origin to 0.75 dn/modius at destination. This is not a direct Augustan quote; it is a calibration built from the earlier wheat anchor and the known need for freight, storage, and merchant margin.
- Annona effect. Private grain trade remains viable because the state relied on private shippers, merchants, warehouse owners, and contractors, but ordinary speculative margin is constrained. In game terms, annona pressure should reduce upside and increase seizure/contract-event risk rather than eliminate grain commerce.
- Horreum rental. Storage buildings are well attested; rental rates are not securely recoverable for 14 BCE. The model uses a small monthly charge because storage matters mechanically but should not dominate the grain equation.
Simulator constants
GRAIN_UNIT_MODII = 100.00
GRAIN_ORIGIN_PRICE_PER_MODIUS_DN = 0.50
GRAIN_DEST_PRICE_PER_MODIUS_DN = 0.75
GRAIN_ORIGIN_PURCHASE_100_DN = 50.00
GRAIN_LOADING_ORIGIN_100_DN = 2.00
GRAIN_SEA_FREIGHT_100_DN = 8.00
GRAIN_PORTORIA_RATE = 0.025
GRAIN_UNLOADING_DEST_100_DN = 2.00
GRAIN_HORREUM_MONTH_100_DN = 1.50
GRAIN_SPOILAGE_RATE = 0.02
GRAIN_DEST_WHOLESALE_100_DN = 75.00
GRAIN_NET_MARGIN_100_DN = 8.125
GRAIN_PRIVATE_MARGIN_RATE = 0.1083
Recommended equation:
grain_total_cost_100_dn =
GRAIN_ORIGIN_PURCHASE_100_DN
+ GRAIN_LOADING_ORIGIN_100_DN
+ GRAIN_SEA_FREIGHT_100_DN
+ (GRAIN_DEST_WHOLESALE_100_DN * GRAIN_PORTORIA_RATE)
+ GRAIN_UNLOADING_DEST_100_DN
+ GRAIN_HORREUM_MONTH_100_DN
+ (GRAIN_DEST_WHOLESALE_100_DN * GRAIN_SPOILAGE_RATE)
= 66.875 dn
grain_net_margin_100_dn = GRAIN_DEST_WHOLESALE_100_DN - grain_total_cost_100_dn
= 8.125 dn
Confidence register
| Model value | Confidence | Reason |
|---|---|---|
| Grain as bulk sea-freight commodity | HIGH | Strong ancient and modern evidence. |
| Destination wheat at 0.75 dn/modius | MEDIUM | Inherited simulator midpoint, defensible but not exact. |
| Origin wheat at 0.50 dn/modius | LOW–MEDIUM | Plausible spread, not directly attested for this scenario. |
| Sea freight at 8 dn / 100 modii | MEDIUM | Supported by Rickman’s ratio logic, though later schedules are used. |
| Horreum rental at 1.5 dn/month/100 modii | LOW | Storage is secure; rental rate is not. |
| Net margin 8.125 dn | MEDIUM | Arithmetic is firm; input confidence is mixed. |
Open questions / calibration flags
- Grain route profitability must remain lower than luxury or specialist goods; if game routes currently produce high grain margins, reduce them.
- Annona-related events should sometimes override private market pricing: requisition, contract, subsidy, delay, or inspection.
- Portoria may need exemption logic for state grain or contracted annona cargo.
- Grain storage cost is the weakest component. Treat
GRAIN_HORREUM_MONTH_100_DNas a tunable constant.
Good 3 — Amber (sucinum / electrum)
Amber is economically distinctive because the Roman merchant does not participate in production and may not know the true origin chain. It stress-tests import-only acquisition, multi-intermediary markup, luxury portability, theft risk, and information asymmetry. The primary source challenge is that Pliny gives important cultural and origin testimony but not a clean raw-amber price list by weight. Therefore the model begins at the Roman acquisition point and treats Baltic origin as database knowledge, not actor knowledge.
Baseline assumptions
- Product: raw Baltic amber, unworked or minimally worked.
- Unit: one Roman libra, approximately 327 g.
- Acquisition point: Aquileia or a northern Italian market.
- End market: Rome, Capua, or another high-demand Italian urban market.
- The Roman merchant’s cost chain begins at acquisition, not at Baltic origin.
Architectural annotation — not a cost component
amber.origin_h3_r5 = Baltic coastal / Maglemoisian occ_flag cells
actor_knows_origin = false
simulator_knows_origin = true
The TESSERA database may track the true prehistoric/ecological origin. The merchant only observes a portable luxury material bought from an intermediary. This is important for mercatus_scientia, periculum_tolerantia, and journal flavor, but it must not create visible origin-cost rows for the player.
Cost components
| Component | Amount (dn or as) | Source | Confidence | Notes |
|---|---|---|---|---|
| Acquisition price at Roman market, raw amber, per libra | 25.00 dn | Pliny, Natural History 37; Tacitus, Germania 45; modern amber-route syntheses including Lundgren, The Gold of the North (2018). | LOW | No secure raw-price tariff. Value is a simulator acquisition price for one libra of desirable raw amber at Aquileia. |
| Number of intermediary hands | 4–7 hands | Pliny, Natural History 37; Tacitus, Germania; scholarship on Amber Road exchange networks. | MEDIUM | Baltic gatherers, local tribal exchange, Danubian/Celtic/Germanic intermediaries, northern Italian merchants. Roman buyer cannot verify the count. |
| Transport from Aquileia / northern Italy to end market | 2.00 dn | Rickman on land transport expense; Casson and general Roman road-freight studies; no direct amber freight tariff. | LOW | Amber is light and portable; cost is more guard/handling/time than bulk freight. |
| Portoria on Italic roads | 1.00 dn | Default 2.5% ad valorem applied to 40 dn retail value. | MEDIUM | Portable luxury goods are appropriate for ad valorem tolling. Use route-level toll points if implemented. |
| Storage for seasonal market timing | 0.50 dn | No direct source — simulator calibration. | LOW | Amber does not spoil; storage is opportunity cost and secure holding. |
| Risk premium: theft-attractive portable luxury | 2.00 dn | No direct source — simulator calibration; informed by Roman legal/commercial risk and luxury portability. | LOW | 5% of 40 dn retail. Represents guards, trusted carriers, concealment, or insurance-like margin. |
| Retail price in Roman market, raw amber, per libra | 40.00 dn | Pliny, Natural History 37; Lundgren; modern discussions of amber as luxury equivalent to gems. | LOW | Raw amber is modeled below worked amber. Worked amber can multiply value by 2–4 depending on piece, skill, and fashion. |
| Worked amber premium | 2.0–4.0 × raw value | Pliny, Natural History 37; archaeological amber ornaments and luxury-good studies. | LOW | Do not apply to the raw-amber baseline. Use later for carved beads, amulets, or figurines. |
Pliny origin and value notes
Pliny’s useful testimony is not a price schedule; it is a knowledge and luxury-status anchor. He explains amber as an exudation from trees, connects it with northern routes and prior misinformation, and treats some amber objects as extravagantly valuable. A compliant short quotation useful for the model: “even our forebears believed it to be a sucus,” i.e. a tree exudation. Another: amber, when rubbed, “attracts straw” like a magnet. These quotes support origin-knowledge and perceived magical/physical value, not a direct price constant.
Specific findings
- Amber Road organization. The Augustan-period Roman buyer should be modeled as buying from a northern Italian or Adriatic intermediary, not from Baltic producers. The chain is multi-handed and opaque.
- Raw amber price evidence. No secure raw-amber-by-libra Augustan price has been found. The
25 dnacquisition and40 dnretail constants are explicit simulator calibrations. - Roman understanding. Pliny and Tacitus show that elite Roman writers had some correct natural-origin understanding by the first century CE, but ordinary merchants need not have operational origin knowledge.
- Information asymmetry. Do not model origin ignorance as a literal cost component. Model it as wider risk premium, higher markup variance, and weaker confidence in quality.
Simulator constants
AMBER_UNIT_LIBRA_GRAMS = 327.00
AMBER_ACQUISITION_RAW_LIBRA_DN = 25.00
AMBER_INTERMEDIARY_HANDS_MIN = 4
AMBER_INTERMEDIARY_HANDS_MAX = 7
AMBER_TRANSPORT_AQUILEIA_ROME_DN = 2.00
AMBER_PORTORIA_RATE = 0.025
AMBER_STORAGE_SEASON_DN = 0.50
AMBER_RISK_PREMIUM_RATE = 0.05
AMBER_RAW_RETAIL_LIBRA_DN = 40.00
AMBER_WORKED_MULTIPLIER_LOW = 2.00
AMBER_WORKED_MULTIPLIER_HIGH = 4.00
AMBER_ACTOR_KNOWS_ORIGIN = false
Recommended equation:
amber_total_cost_dn =
AMBER_ACQUISITION_RAW_LIBRA_DN
+ AMBER_TRANSPORT_AQUILEIA_ROME_DN
+ (AMBER_RAW_RETAIL_LIBRA_DN * AMBER_PORTORIA_RATE)
+ AMBER_STORAGE_SEASON_DN
+ (AMBER_RAW_RETAIL_LIBRA_DN * AMBER_RISK_PREMIUM_RATE)
= 30.50 dn
amber_net_margin_dn = AMBER_RAW_RETAIL_LIBRA_DN - amber_total_cost_dn
= 9.50 dn
Confidence register
| Model value | Confidence | Reason |
|---|---|---|
| Import-only Roman acquisition model | HIGH | Correct structure for a Roman merchant buying amber in Italy. |
| Intermediary chain 4–7 hands | MEDIUM | Historically plausible; exact count unknowable. |
| Raw acquisition at 25 dn/libra | LOW | Required calibration; not directly attested. |
| Raw retail at 40 dn/libra | LOW | Required calibration; bounded by luxury status, not by price list. |
| Risk premium 5% | LOW | Mechanically useful, historically plausible, not directly attested. |
| Actor does not know true origin H3 | HIGH | Architectural rule from brief; fits information-asymmetry model. |
Open questions / calibration flags
- Raw amber needs a quality system. Transparent tawny pieces should price above cloudy or waxy material.
- Amber should have high markup variance because quality and story dominate value.
- Worked amber must be a separate downstream craft good, not a simple transport variant.
- Information asymmetry should modify risk and negotiation, not appear as a visible “origin cost.”
Good 4 — Marble Architectural Element
A Luna marble Corinthian capital is economically distinctive because it is a single custom commission, not a batch good. It stress-tests quarry access, specialist stone labour, heavy-cargo transport, river transshipment, breakage risk, and a patron-agent-workshop relationship in which the merchant organizes rather than manufactures. The primary source challenge is that quarry ownership, marble prices, and transport organization are much better attested in the imperial period than specifically in 14 BCE. The model therefore uses Luna marble’s Augustan relevance and later Roman marble-trade studies to build a defensible commission equation.
Baseline assumptions
- Product: one Corinthian column capital in Luna/Carrara marble.
- Finished weight: 400 kg; quarry block before reduction: approximately 700 kg.
- Commission context: wealthy patron in Rome contracts through a merchant-agent/factor.
- Merchant role: organizer of commission, payments, transport, and delivery, not manufacturer.
- Transport chain: quarry → ox-cart to coast → sea freight to Ostia → Tiber barge to Rome.
Cost components
| Component | Amount (dn or as) | Source | Confidence | Notes |
|---|---|---|---|---|
| Quarry block purchase / quarry access | 60.00 dn | J. Clayton Fant, Cavum Antrum Phrygiae and Roman marble-trade studies; Patrizio Pensabene on Roman marble; Luna marble archaeology. | LOW | No secure Augustan block price for a capital-grade piece. Value assumes high-quality local Italian marble, not exotic imported colored stone. |
| Quarrying labour, extraction | 12.00 dn | Baseline skilled wage doubled for stone specialists; general quarrying studies; Fant. | LOW | 6 days × 2 dn/day specialist crew-equivalent. Hazardous extraction earns premium over ordinary craft wage. |
| Rough-shaping at quarry | 20.00 dn | Stone transport logic in Fant and Roman quarry studies; archaeological evidence for reducing weight near source. | LOW | Reduces transport weight and breakage risk. Includes rough blocking and removal of excess stone. |
| Final Corinthian carving | 120.00 dn | No direct source — simulator calibration; informed by sculptural labour complexity, specialist carvers, and architectural ornament studies. | LOW | 8 weeks of skilled/specialist labour plus assistant time. This is the dominant craft cost. |
| Transport: quarry to coast by ox-cart | 30.00 dn | Rickman on land transport expense; A. M. Burford on heavy transport; Fant on marble transport difficulty. | LOW | Heavy stone by land is expensive even over short distances. Use route-distance multiplier if implemented. |
| Sea freight: coast to Ostia | 12.00 dn | Casson, Ships and Seamanship; Fant, “Contracts and costs for shipping marble”; Roman heavy-cargo studies. | LOW–MEDIUM | Stone is dense and weight-priced. Sea movement is cheaper than road but handling is difficult. |
| River barge: Ostia to Rome | 6.00 dn | Casson; Roman Tiber transport studies; Ostia/Portus logistics. | LOW | Short river leg, heavy cargo, specialized handling. |
| Portoria at toll points | 10.00 dn | Default 2.5% ad valorem applied to 400 dn commission value, unless exempt. | MEDIUM | Use as route-level ad valorem. Luxury commission may face multiple fiscal frictions, but avoid stacking duplicate tolls unless route requires. |
| Agent / factor fee | 40.00 dn | Roman agency and commerce studies: Andreau, Banking and Business in the Roman World; Terpstra, Trade in the Roman Empire. | LOW | Modeled as 10% of 400 dn patron commission. This is the merchant’s organizing margin, not production cost. |
| Breakage / damage risk premium | 20.00 dn | No direct source — simulator calibration; informed by heavy stone transport and repair/replacement risk. | LOW | 5% of commission value. Represents insurance-like margin, contractual buffer, and handling risk. |
| Total commission value to patron | 400.00 dn | No direct source — simulator calibration; bounded by elite architectural expenditure and craft/transport burden. | LOW | Suitable for a wealthy patron commission; not a public-monument scale. |
| Total non-agent cost | 290.00 dn | Derived. | MEDIUM | Sum excluding 40 dn agent fee and 20 dn risk reserve: 60 + 12 + 20 + 120 + 30 + 12 + 6 + 10 + 20 = 290 if risk included; 270 without risk. |
| Merchant gross margin / reserve | 110.00 dn | Derived. | MEDIUM | 400 - 290 = 110 dn; of this, 40 dn is explicit fee, 20 dn risk reserve, 50 dn contingency/profit. |
Specific findings
- Luna marble pricing. Luna marble is appropriate for Augustan Italy, but block prices at the quarry face are not securely preserved. Quarry block purchase is therefore calibration, not reconstruction.
- Carver rates. Architectural stone-carver daily rates for 14 BCE are not directly available. The model uses a specialist premium above the 1 dn/day skilled-artisan baseline.
- Transport. Heavy stone validates the model’s distinction between volume cargo and weight cargo. Land haul dominates over short distance; sea and river remain cheaper but require handling risk.
- Patron-agent-workshop risk. The merchant is exposed to overruns, damage, patron specification changes, and late delivery. This should be modeled as a commission reserve and risk premium rather than ordinary inventory margin.
Simulator constants
MARBLE_CAPITAL_FINISHED_WEIGHT_KG = 400.00
MARBLE_CAPITAL_BLOCK_WEIGHT_KG = 700.00
MARBLE_BLOCK_PURCHASE_DN = 60.00
MARBLE_QUARRYING_LABOUR_DN = 12.00
MARBLE_ROUGH_SHAPING_DN = 20.00
MARBLE_FINAL_CARVING_DN = 120.00
MARBLE_QUARRY_TO_COAST_TRANSPORT_DN = 30.00
MARBLE_SEA_FREIGHT_TO_OSTIA_DN = 12.00
MARBLE_TIBER_BARGE_DN = 6.00
MARBLE_PORTORIA_RATE = 0.025
MARBLE_AGENT_FEE_RATE = 0.10
MARBLE_BREAKAGE_RISK_RATE = 0.05
MARBLE_PATRON_COMMISSION_DN = 400.00
Recommended equation:
marble_direct_cost_dn =
MARBLE_BLOCK_PURCHASE_DN
+ MARBLE_QUARRYING_LABOUR_DN
+ MARBLE_ROUGH_SHAPING_DN
+ MARBLE_FINAL_CARVING_DN
+ MARBLE_QUARRY_TO_COAST_TRANSPORT_DN
+ MARBLE_SEA_FREIGHT_TO_OSTIA_DN
+ MARBLE_TIBER_BARGE_DN
+ (MARBLE_PATRON_COMMISSION_DN * MARBLE_PORTORIA_RATE)
= 270.00 dn
marble_agent_fee_dn = MARBLE_PATRON_COMMISSION_DN * MARBLE_AGENT_FEE_RATE
= 40.00 dn
marble_breakage_reserve_dn = MARBLE_PATRON_COMMISSION_DN * MARBLE_BREAKAGE_RISK_RATE
= 20.00 dn
marble_total_exposure_dn = marble_direct_cost_dn + marble_breakage_reserve_dn
= 290.00 dn
marble_net_agent_margin_dn = MARBLE_PATRON_COMMISSION_DN - marble_total_exposure_dn
= 110.00 dn
Confidence register
| Model value | Confidence | Reason |
|---|---|---|
| Luna marble as Augustan elite material | HIGH | Strong archaeological/historical support. |
| Merchant as factor/agent rather than manufacturer | MEDIUM | Fits Roman commerce and commission logic; specific contract form varies. |
| Block purchase 60 dn | LOW | Required calibration; no exact Augustan price. |
| Final carving 120 dn | LOW | Labour-intensive and plausible, but not directly attested. |
| Heavy land transport premium | MEDIUM | Strong qualitative support; exact rate uncertain. |
| Commission value 400 dn | LOW | Simulator calibration for wealthy private commission. |
| 5% breakage reserve | LOW | Mechanically useful; no secure rate for damaged stone shipments. |
Open questions / calibration flags
- If the patron is extremely elite, the 400 dn commission may be too low; keep this as a “private decorative element,” not temple-scale architecture.
- Imperial quarry control becomes more important after Augustus; avoid assuming fully imperial quarry administration for 14 BCE unless route/event explicitly says so.
- If route engine supports weight, marble should use weight-based freight, not amphora-equivalent freight.
- Cost overruns should be event-driven: miscut block, delayed carver, broken acanthus detail, river delay, patron changes specification.
Cross-good calibration notes
-
Portoria default remains usable, but exemptions matter. The 0.025 ad valorem default works across garum, grain, amber, marble, and transported ceramics. Grain is the main exception: annona-linked or contracted cargo may be exempt, subsidized, or administratively constrained. Do not raise the global default merely because a single route implies multiple toll frictions.
-
Sea freight and land freight must remain separate cost families. Grain and garum validate sea freight as efficient at scale. Marble validates the opposite: short land segments can dominate total transport because heavy stone moves badly over roads. Amber shows that portable luxury goods do not pay much physical freight but do carry risk and information costs.
-
The ceramic cup remains the correct humble baseline. Its 2-as local retail price would be destroyed by long-distance individual transport. This is useful: the model should trade ceramics in batches or as amphora/container supply, not as single-item arbitrage.
-
Grain margins should be lower than current game-style route margins. The grain model yields roughly 10.8% after ordinary costs. If OTIVM route cards show grain profits of 40–70%, those should be interpreted as early-game abstraction, rare scarcity, or mixed cargo — not ordinary private grain trade under annona pressure.
-
Garum introduces quality-tier multiplication. Common garum and luxury
garum sociorumdiffer by orders of magnitude. The simulator needs aquality_grademultiplier for some goods; not all goods scale linearly with weight or volume. -
Amber introduces hidden-origin modeling. Amber’s true origin belongs in TESSERA/occ_flag architecture, not the actor-visible cost model. For the actor, amber is an acquisition-price good with risk and uncertainty. This creates a clean split between world truth and merchant knowledge.
-
Marble introduces commission economics. The merchant does not buy low and sell high in the ordinary sense. He organizes a contract, advances or coordinates payments, and absorbs completion risk. This requires a distinct
commissionroute pattern withagent_fee,risk_reserve, andcontingency_margin. -
Open consistency issue: labour rates. The inherited
WAGE_SKILLED_ARTISAN_DN = 1.00works for ceramic and ordinary craft. Garum specialists, stonecutters, and carvers require multipliers above this baseline. Recommended multiplier table:
LABOUR_MULTIPLIER_UNSKILLED = 1.00 // 0.50 dn/day
LABOUR_MULTIPLIER_SKILLED_STANDARD = 1.00 // 1.00 dn/day
LABOUR_MULTIPLIER_SPECIALIST_FOOD = 1.20 // garum maker
LABOUR_MULTIPLIER_STONECUTTER = 2.00
LABOUR_MULTIPLIER_SCULPTOR_DETAIL = 2.50
- Recommended product-pattern taxonomy after five goods.
| Pattern | Baseline good | Core equation |
|---|---|---|
| Humble local batch craft | Ceramic cup | raw + labour + kiln + overhead + market |
| Specialist perishable batch | Garum | raw + salt + vessel + time + spoilage + quality |
| Bulk staple sea cargo | Grain | origin price + freight + storage + loss + low margin |
| Import-only portable luxury | Amber | acquisition + risk + information asymmetry + markup |
| Custom heavy commission | Marble capital | block + labour + heavy transport + agent fee + risk reserve |
- Recommended schema implication. Add or reserve these model fields for future goods:
good_pattern // batch_craft, perishable_batch, bulk_staple, import_luxury, commission_heavy
quality_grade // common, fine, luxury, imperial, raw, worked
spoilage_rate // nullable; applies to food/perishables/grain
risk_premium_rate // theft/damage/completion risk
actor_knows_origin // boolean; important for amber-like goods
commission_mode // boolean; important for marble-like goods
freight_basis // item, volume, weight, modius, amphora, libra
Bibliography and evidence notes
Ancient evidence
- Pliny the Elder, Natural History 31.93–95. Fish sauces, salt, and luxury garum testimony. Used primarily to anchor the existence and elite price ceiling of luxury fish sauce.
- Pliny the Elder, Natural History 37.30–51. Amber origin, properties, northern route knowledge, luxury status. Used for amber knowledge and value framing, not direct raw-price tariff.
- Tacitus, Germania 45. Baltic amber collection and Germanic trade context. Used for amber intermediary framing.
- Suetonius, Augustus. Grain-supply governance context and Augustan intervention background.
- Diocletian, Edict on Maximum Prices (AD 301). Used only as later Roman relative-price and wage evidence, not as direct 14 BCE pricing.
Modern evidence and synthesis
- Robert I. Curtis, Garum and Salsamenta: Production and Commerce in Materia Medica, Brill, 1991.
- Sally Grainger, The Story of Garum: Fermented Fish Sauce and Salted Fish in the Ancient World, Routledge, 2021.
- Annalisa Marzano, Harvesting the Sea: The Exploitation of Marine Resources in the Roman Mediterranean, Oxford University Press, 2013.
- Geoffrey Rickman, The Corn Supply of Ancient Rome, Oxford University Press, 1980.
- Geoffrey Rickman, Roman Granaries and Store Buildings, Cambridge University Press, 1971.
- Paul Erdkamp, The Grain Market in the Roman Empire: A Social, Political and Economic Study, Cambridge University Press, 2005.
- Lionel Casson, Ships and Seamanship in the Ancient World, Princeton University Press, 1971.
- Richard Duncan-Jones, The Economy of the Roman Empire: Quantitative Studies, 2nd ed., Cambridge University Press, 1982.
- Peter Temin, The Roman Market Economy, Princeton University Press, 2013.
- Jean Andreau, Banking and Business in the Roman World, Cambridge University Press, 1999.
- Taco T. Terpstra, Trade in the Roman Empire: A Study of the Institutional Framework, Columbia University dissertation, 2011.
- J. Clayton Fant, “Ideology, Gift, and Trade: A Distribution Model for Roman Imperial Marbles,” and related Roman marble-trade studies.
- J. Clayton Fant, “Contracts and Costs for Shipping Marble in the Roman Empire.”
- Patrizio Pensabene, studies on Roman marble quarrying, distribution, and architectural decoration.
- Hazel Dodge and Bryan Ward-Perkins, eds., Marble in Antiquity: Collected Papers of J. B. Ward-Perkins, British School at Rome, 1992.
- Ole Lundgren, The Gold of the North: Amber in the Roman Empire, 2018.
- Ellen Swift, work on amber beads and Roman/Germanic material culture, cited in amber-route scholarship.