In microeconomics, in a standard trade model with two products, an isovalue line is the vector of combinations for which the market value of total production is constant. The formula for isovalue line V is:
V = Q x P x + Q y P y {\displaystyle V=QxPx+QyPy}
in which: Q is quantity P is price x and y are products. For example: Assume an economy that only produces bread and wine and in which relative prices are fixed, say one bottle of wine equals the price of three breads. The isovalue line V (in a graph with bread as x and wine as y) slopes less than 45° downward. The exact slope is derived from the wine/bread price relation, in this case -1/3.
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