Dr(p) = D(p) – So(p).
At prices so high that So(p) is greater than D(p), the residual demand, Dr(p), is zero.
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Residual Demand Curve. The residual demand curve, Dr(p), a single office furniture manufacturing firm faces is the market demand, D(p), minus the supply of the other firms in the market, So(p). The residual demand curve is much flatter than the market demand curve.
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In the figure, we derive the residual demand for a Canadian manufacturing firm that produces metal chairs. Panel b shows the market demand curve, D, and the supply of all but one manufacturing firm, So.1 At p = $66 per chair, the supply of other firms, 500 units (one unit being 1,000 metal chairs) per year, exactly equals the market demand (panel b), so the residual quantity demanded of the remaining firm (panel a) is zero.
At prices below $66, the other chair firms are not willing to supply as much as the market demands. At p = $63, for example, the market demand is 527 units, but other firms want to supply only 434 units. As a result, the residual quantity demanded from the individual firm at p = $63 is 93 (= 527 - 434) units. Thus, the residual demand curve at any given price is