Why this is mistaken
A binding ceiling lowers the permitted posted price in the simple model, but it also creates excess demand. The model must specify which buyers receive units. Search, queues, side payments, reduced quality, eligibility, and enforcement can change effective cost and incidence.
Repair the analysis with a rationing ledger: eligible buyers, short-side traded quantity, allocation rule, time and search cost, side terms, quality, unserved buyers, enforcement, and distribution. Compute consumer surplus only under the declared allocation assumption.
The corrected conclusion can find gains for some buyers without claiming every buyer gains or that posted price equals full economic cost.
Where to watch
When this mistake may appear
- A maximum price lies below modeled equilibrium.
- Quantity demanded exceeds quantity supplied at the cap.
Check your work
Your work may contain this mistake if:
- Says every buyer pays less and gains.
- Ignores who receives the short-side quantity.
- Treats posted price as the full effective cost despite queues, fees, or quality changes.