The Gains from Free Trade at Home With Home demand of D and supply of S, the no-trade equilibrium is at point A, at the price P^A producing Q₀. With free trade, the world price is P^W, so quantity demanded increases to D₁ and quantity supplied falls to S₁. Since quantity demanded exceeds quantity supplied, Home imports D₁ − S₁. Consumer surplus increases by the area (b + d), and producer surplus falls by area b. The gains from trade are measured by area d.