COMSCI/ECON 206 · PS1 interactive companion

Farmer Margin Rule Lab

Explore how a platform's margin rule can shape intermediary effort, farmer participation, household purchases, and surplus in a hypothetical underserved market.

Interpret carefully: this is an inspectable synthetic model, not evidence about real farmers or a policy recommendation. Change one assumption at a time to see what drives the result.

Choose assumptions

PS1 baseline: farmer payment w = 6, unit cost c = 4, household valuation gap = 4.

Model and decision rule

q = D × r × e × max(0, 4 − m)
pi_F = (6 − 4)q − K
pi_I = mq − lambda e²

For a fixed margin, the model searches effort from 0 to 1. For a chosen margin, it searches margins from 0 to 4 and effort from 0 to 1. The farmer group participates only when net earnings are nonnegative. This is a transparent grid search, not a trained AI model or a field estimate.

Synthetic outcome

Cards show the highlighted rule; the table compares both rules under identical assumptions.

Selected margin
Intermediary effort
Retail price
Completed purchases
Farmer net earnings
Intermediary profit

RuleMarginEffortPurchasesFarmer netIntermediary profitParticipation
Reflection prompt

If coordination cost rises while all other assumptions remain unchanged, farmer participation is most directly at risk: K reduces farmer net earnings and can cause the group to exit.