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For First Responders · Supply & Demand

Supply & Demand for an externality

Built for first responders planning or training for real incidents. Run fast what-if scenarios for response planning and training — no software to install in the field. Simulate an externality live below — adjust the inputs and watch it respond, right in your browser.

Supply & DemandLive

market equilibrium & surplus

Controls

Presets

Demand shift

Supply shift

Per-unit tax

Where the downward demand curve crosses the upward supply curve, the market clears: that price and quantity are the equilibrium. Shifting either curve moves it. The shaded triangles are consumer and producer surplus — the total gains from trade. A per-unit tax lifts the supply curve, raising price, cutting quantity, and creating deadweight loss.

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Data Inspector

Equilibrium price$60.0

Equilibrium qty40.0

Consumer surplus800

Producer surplus800

Governing equation

P_{d} = 100 - 1 Q, P_{s} = 20 + 1 Q \Rightarrow Q^{*} = \frac{a - c}{b + d} = 40.0, P^{*} = 60.0

Reading this result: At the free-market equilibrium of $60.0, 40.0 units clear and the combined surplus (1600) is maximized.

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Frequently asked questions

Is this good for first responders?: Yes — this version of "Supply & Demand for an externality" is framed for first responders planning or training for real incidents. Run fast what-if scenarios for response planning and training — no software to install in the field.
Do I need to install anything?: No. It runs in any modern browser, free, with no account required.