Producer's Equilibrium

Just as a consumer aims for maximum satisfaction, a producer (firm) aims for maximum profit. A producer is in equilibrium when he produces that level of output which gives him the maximum profit and has no tendency to change his output (neither to increase nor to decrease it).

Profit is the difference between the firm's total revenue and its total cost:

Profit = Total Revenue (TR) − Total Cost (TC)

The firm wants to make this gap as large as possible. So producer's equilibrium is the output at which the difference between TR and TC is the greatest — the point of maximum profit.

Why does the firm settle at one particular output? Because as it changes output, profit changes. If producing one more unit adds more to revenue than to cost, profit rises, so the firm expands. If one more unit adds more to cost than to revenue, profit falls, so the firm cuts back. The firm keeps adjusting until it reaches the output where profit can rise no further — that is its equilibrium. There are two equivalent ways to find this output: the TR–TC approach and the MR–MC approach, which we study next.

The first way to find the profit-maximising output is the Total Revenue–Total Cost (TR–TC) approach. The idea is simple: calculate profit (TR − TC) at each level of output, and choose the output where this difference is the largest.

Consider this table:

Here profit is highest (₹8) at an output of 3 units, so that is the producer's equilibrium. Below 3 units the firm could earn more by producing more; above 3 units profit starts to fall. The firm settles where the gap between TR and TC is widest. (This price is constant at ₹10, so TR rises in a straight line; the TR–TC approach works whether price is constant or falling.) The TR–TC approach is the most direct, but for analysis economists often prefer the marginal (MR–MC) approach, which we study next.

The second and more analytical way to find equilibrium is the Marginal Revenue–Marginal Cost (MR–MC) approach. Recall: MR is the addition to revenue from one more unit, and MC is the addition to cost from one more unit. The firm should keep producing as long as each extra unit adds more to revenue than to cost.

• If MR > MC, the extra unit adds more to revenue than to cost, so profit rises — the firm should produce more.
• If MR < MC, the extra unit adds more to cost than to revenue, so profit falls — the firm should produce less.
• Profit is maximum where MR = MC.

But MR = MC alone is not enough — there are two conditions for producer's equilibrium:

1. MR = MC (the marginal revenue equals the marginal cost).
2. MC must be rising at that point — i.e. the MC curve must cut the MR curve from below. (MR and MC can be equal at two points; profit is maximised only at the one where MC is rising. At the other point, where MC is falling, producing more would still raise profit.)

Both approaches give the same equilibrium output. The TR–TC approach finds where the profit gap is widest; the MR–MC approach finds where the last unit just breaks even at the margin (MR = MC, MC rising). The marginal approach is preferred because it shows clearly why the firm stops at that exact output: the very last unit it makes adds exactly as much to revenue as to cost.