Expansion path
![Isocost v. Isoquant Graph. Each line segment is an isocost line representing one particular level of total input costs, denoted TC, with PL being the unit price of labor and PK the unit price of physical capital. The convex curves are isoquants, each showing various combinations of input usages that would give the particular output level designated by the particular isoquant. Tangency points show the lowest cost input combination for producing any given level of output. A curve connecting the tangency points is called the expansion path because it shows how the input usages expand as the chosen level of output expands.](/Images/godic/202501/12/Isoquant_isocost_graph4645.gif")
In economics, an expansion path (also called a scale line) is a curve in a graph with quantities of two inputs, typically capital and labor, plotted on the axes. The path connects optimal input combinations as the scale of production expands. A producer seeking to produce the most units of a product in the cheapest possible way attempts to increase production along the expansion path.