Business Economics (Micro) व्यावसायिक अर्थशास्त्र

Quick summary

Costs are what a firm spends on producing output; revenue is what it earns by selling it. A firm's profit and its output decisions depend on how costs and revenues change with output. This topic explains the main cost concepts, short-run and long-run cost curves, and total, average and marginal revenue under different markets.

Key points

• Cost (खर्च) concepts: money cost and real cost; explicit (paid out) and implicit (imputed, e.g. owner's own capital) cost; opportunity cost; private and social cost; fixed and variable cost.
• Economic cost = explicit + implicit cost, so economic profit is less than accounting profit.
• Short run: total cost = total fixed cost (rent, salaries, insurance; constant even at zero output) + total variable cost (raw materials, power, wages; varies with output).
• AFC keeps falling as output rises (a rectangular hyperbola). AVC, ATC and MC are U-shaped because of the Law of Variable Proportions.
• MC cuts AVC and ATC at their minimum points. When MC < AC, AC falls; when MC > AC, AC rises.
• Long-run average cost (LAC) is the "envelope" of short-run AC curves; it is U-shaped (flatter) because of economies and then diseconomies of scale. It is also called the planning curve.
• Revenue (महसूल): TR = P × Q; AR = TR/Q = price; MR = change in TR from one more unit.
• Under perfect competition price is constant, so AR = MR and both are a horizontal line.
• Under monopoly and monopolistic competition, the firm must lower price to sell more, so AR slopes down and MR lies below AR.
• Profit is maximum where MR = MC and MC is rising (cuts MR from below).

Important terms

• Fixed cost – does not change with output in the short run.
• Variable cost – changes directly with output.
• Marginal cost (MC) – addition to total cost from one more unit.
• Sunk cost – cost already incurred that cannot be recovered.
• Break-even point – where TR = TC (no profit, no loss).

Formats and formulas

• TC = TFC + TVC; AFC = TFC/Q; AVC = TVC/Q; ATC = TC/Q = AFC + AVC
• MCn = TCn − TC(n−1)
• TR = P × Q; AR = TR/Q; MRn = TRn − TR(n−1)
• Relation (elasticity e): MR = AR × (e − 1)/e

Worked cost table (TFC = ₹100):

MC is lowest at 3 units; MC (40) equals AVC (40) at its minimum at 4 units; ATC is still falling at 5 units because MC (60) is below ATC (64).

Revenue when price must fall to sell more:

5 important questions

Q1. Distinguish between fixed cost and variable cost.

Fixed cost stays the same at all levels of output in the short run and must be paid even at zero output (rent, interest, permanent salaries). Variable cost changes with output and is zero when output is zero (raw materials, power, casual wages).

Q2. Why is the AFC curve always falling?

Because a constant total fixed cost is spread over more and more units as output rises; AFC = TFC/Q falls continuously but never touches the x-axis.

Q3. Explain short-run cost curves with a diagram.

Outline: table like the one above → TFC (horizontal), TVC and TC (parallel, rising) → AFC, AVC, ATC, MC → why AVC/ATC/MC are U-shaped (variable proportions) → MC cuts AVC and ATC at their minimum → gap between ATC and AVC = AFC, narrowing as output grows.

Q4. Explain the long-run average cost curve.

Outline: in the long run all factors vary → several plant sizes, each with an SAC → LAC is the envelope touching each SAC → U-shape due to economies, then diseconomies of scale → flatter than SAC → also called planning curve.

Q5. Explain the relation between AR and MR under perfect and imperfect competition.

Outline: definitions → perfect competition: price fixed, AR = MR, horizontal line (table with price ₹10) → monopoly/monopolistic competition: AR falls, MR falls faster and lies below AR, MR can become negative → formula MR = AR(e − 1)/e → diagrams.

Exam tip

Fill a cost or revenue table yourself in the exam even if not asked; it proves the shape of every curve you draw.

Quick summary

Perfect competition is a market with a very large number of buyers and sellers dealing in an identical product, where no single firm can influence the price. The price is fixed by industry demand and supply, and each firm is a price-taker. This topic covers the features of perfect competition, how price is determined, and the short-run and long-run equilibrium of the firm and the industry.

Key points

• Features: large number of buyers and sellers, homogeneous product, free entry and exit, perfect knowledge, perfect mobility of factors, no transport cost, no government interference.
• Pure competition has only the first three features; perfect competition has all.
• The industry is a price-maker; the firm is a price-taker. The firm's demand (AR) curve is perfectly elastic (horizontal), and AR = MR = Price.
• Price is determined where the industry's demand equals supply (Marshall's "scissors": both blades — demand and supply — matter).
• Time element (Marshall): market period (supply fixed, demand decides price), short period, long period.
• Conditions of firm's equilibrium: MR = MC, and MC must be rising (MC cuts MR from below).
• Short run: a firm may earn super-normal profit (AR > ATC), normal profit (AR = ATC) or a loss (AR < ATC).
• A firm continues production in the short run as long as price ≥ AVC. The point where price = minimum AVC is the shut-down point.
• Long run: free entry and exit remove super-normal profit and losses, so every firm earns only normal profit: Price = AR = MR = MC = minimum LAC.
• In long-run equilibrium firms produce at the lowest point of LAC (optimum size), so resources are used most efficiently.

Important terms

• Price-taker – a firm that must accept the market price.
• Normal profit (सामान्य नफा) – minimum profit needed to keep the firm in the industry; included in costs.
• Super-normal profit – profit above normal profit.
• Shut-down point – price equal to minimum AVC; below it the firm stops production.
• Break-even point – price equal to minimum ATC.

Formats and formulas

Example: market price ₹20. At the output where MC = 20, ATC = ₹16 and output = 100 units. Profit per unit = 20 − 16 = ₹4; total super-normal profit = 4 × 100 = ₹400. New firms will enter, supply will rise and price will fall until it equals minimum LAC.

5 important questions

Q1. Why is a firm under perfect competition a price-taker?

Because there are so many sellers of an identical product that one firm's output is a tiny part of total supply. If it charges more, buyers go to other sellers; it has no reason to charge less. So it accepts the market price.

Q2. What is the shut-down point?

It is the level of price equal to the minimum average variable cost. Below it the firm cannot even cover its variable costs and stops production in the short run.

Q3. Explain the features of perfect competition.

Outline: list and explain each feature with its effect (large number → price-taker; homogeneous product → single price; free entry → normal profit in the long run; perfect knowledge; mobility; no transport cost) → difference between pure and perfect competition.

Q4. Explain the short-run equilibrium of a firm under perfect competition.

Outline: conditions (MR = MC, MC rising) → three diagrams: super-normal profit, normal profit, loss → shut-down condition with AVC → short-run supply curve is the MC curve above minimum AVC.

Q5. Explain the long-run equilibrium of the firm and the industry.

Outline: entry when profits exist, exit when losses exist → adjustment of price → final position: P = AR = MR = LMC = minimum LAC → only normal profit → optimum size firms → industry equilibrium when no firm wants to enter or leave → diagram.

Exam tip

Draw the industry diagram (demand and supply) beside the firm diagram (horizontal AR = MR) to show where the price comes from; examiners like the two-panel diagram.

Quick summary

Monopoly is a market with a single seller of a product with no close substitute and strong barriers to entry. Monopolistic competition, described by E. H. Chamberlin, has many sellers selling differentiated products (brands) that are close substitutes. This topic covers their features, price-output determination, price discrimination and the role of selling costs.

Key points

• Monopoly (मक्तेदारी) features: single seller, no close substitutes, barriers to entry, price-maker, downward-sloping AR, MR below AR.
• Sources of monopoly: legal rights (patents, licences, copyrights), control of raw materials, huge capital needs, government ownership (Indian Railways), natural monopoly (water supply), mergers and cartels.
• Monopoly equilibrium: MR = MC with MC rising; price is read from the AR curve above that output.
• A monopolist can earn super-normal profit even in the long run because entry is blocked.
• A monopolist always produces on the elastic part of the demand curve (where MR is positive).
• Price discrimination: charging different prices to different buyers for the same product (doctors, railways' AC and sleeper classes, electricity for homes and industry).
• Conditions for price discrimination: separate markets, different elasticities of demand, no resale between markets.
• Monopolistic competition features: many sellers, product differentiation, free entry and exit, selling costs (advertising), some control over price, group (not industry).
• Short run: a firm may earn profit or loss. Long run: free entry removes super-normal profit, AR is tangent to LAC, so only normal profit.
• The firm produces less than the optimum output at the long-run equilibrium; the difference is called excess capacity.

Important terms

• Price-maker – a firm that fixes its own price.
• Product differentiation – making a product appear different by brand, design, packing or service.
• Selling costs – costs to increase demand: advertising, sales promotion, salesmen's salaries.
• Dumping – selling at a lower price abroad than at home (a form of price discrimination).
• Excess capacity – gap between ideal output (minimum LAC) and actual output.

Formats and formulas

Equilibrium rule for all: MR = MC with MC rising. Under price discrimination: MR in market A = MR in market B = MC; higher price in the market with less elastic demand.

5 important questions

Q1. What is price discrimination? Give two examples.

Charging different prices to different buyers for the same good or service, for reasons not linked to cost. Examples: a doctor charging rich and poor patients differently; electricity boards charging different rates for domestic and industrial use.

Q2. What are selling costs?

Expenses incurred to create or increase demand for a product, such as advertising, discounts, free samples, displays and salesmen's salaries. They are an important feature of monopolistic competition.

Q3. Explain price and output determination under monopoly.

Outline: features → AR and MR curves → MC and AC → equilibrium at MR = MC → price from AR → profit area (AR − AC) × Q → short run (profit or even loss) and long run (super-normal profit continues) → diagram.

Q4. Explain the features of monopolistic competition.

Outline: many sellers → product differentiation → free entry → selling costs → independent price policy → non-price competition → concept of group → examples (soaps, toothpaste, restaurants).

Q5. Explain the equilibrium of a firm under monopolistic competition in the short run and long run.

Outline: AR and MR downward and elastic → short run profit or loss diagrams → long run: new brands enter, AR shifts left until tangent to LAC → normal profit → excess capacity → wastes of monopolistic competition (advertising, too many brands).

Exam tip

In any market-form question, write the equilibrium condition MR = MC first, then explain how price is read from the AR curve. This one line shows the examiner you know the logic.

Quick summary

Factor pricing explains how the rewards of the four factors of production are fixed: rent for land, wages for labour, interest for capital and profit for the entrepreneur. The general theory is the Marginal Productivity Theory, and each factor also has its own special theories. This topic covers those theories in short, exam-ready form.

Key points

• General rule: a factor's price is fixed by its demand and supply; the demand for a factor is a derived demand (it comes from demand for the goods it produces).
• Marginal Productivity Theory: under perfect competition, a factor is paid equal to the value of its marginal product (VMP = MRP), and the firm hires it until MRP = factor price.
• Rent (खंड): Ricardian rent is the payment for the "original and indestructible powers of the soil". It arises from differences in fertility and location, and it is a surplus over the marginal (no-rent) land.
• Modern theory of rent: rent is a surplus earned by any factor whose supply is less than perfectly elastic (earnings above transfer earnings).
• Quasi-rent (Marshall): short-run surplus earned by machines and other man-made factors whose supply is fixed for a time = TR − TVC; it disappears in the long run.
• Wages (मजुरी): money wages vs real wages (what money wages can buy). Theories: subsistence theory, wage fund theory, marginal productivity theory, modern demand-and-supply theory; collective bargaining by trade unions also affects wages.
• Interest (व्याज): reward for parting with liquidity or for waiting. Theories: classical (saving = investment), loanable funds theory, and Keynes's liquidity preference theory (transactions, precautionary and speculative motives).
• Profit (नफा): reward of the entrepreneur. Theories: rent theory (Walker), risk theory (Hawley), uncertainty-bearing theory (Knight: only non-insurable uncertainty earns profit), innovation theory (Schumpeter).
• Gross profit includes implicit rent, wages and interest on the owner's resources; net (pure) profit is the reward for enterprise only.

Important terms

• Transfer earnings – minimum payment needed to keep a factor in its present use.
• Economic rent – earnings above transfer earnings.
• Real wage – money wage adjusted for price level and other benefits.
• Liquidity preference – desire to hold wealth in cash.
• Innovation – new product, new method, new market, new source of raw material or new organisation (Schumpeter).

Formats and formulas

• MRP = MP × MR; under perfect competition VMP = MP × Price = MRP
• Firm hires labour till MRP = Wage
• Economic rent = Actual earnings − Transfer earnings
• Quasi-rent = Total revenue − Total variable cost
• Real wage ≈ Money wage ÷ Price index × 100

Ricardian rent example (equal labour and capital on each plot):

Economic rent example: a manager earns ₹80,000 a month; the next-best job offers ₹60,000. Economic rent = 80,000 − 60,000 = ₹20,000.

5 important questions

Q1. What is quasi-rent?

Quasi-rent is the short-run surplus earned by man-made factors (machines, buildings) whose supply cannot be increased quickly. It equals total revenue minus total variable cost and disappears in the long run as supply adjusts.

Q2. Distinguish between money wages and real wages.

Money wages are the wages paid in money. Real wages are what money wages can actually buy, including perks such as free housing, plus job conditions. Real wages depend on the price level, extra benefits, working hours and future prospects.

Q3. Explain the Ricardian theory of rent and its criticism.

Outline: meaning and assumptions (land has original powers, law of diminishing returns, cultivation extends to inferior land) → extensive and intensive margin with a table → rent as differential surplus → rent does not enter price → criticism (no "indestructible" powers, ignores scarcity rent, order of cultivation not always from best to worst).

Q4. Explain the liquidity preference theory of interest.

Outline: Keynes's definition of interest → demand for money: transactions, precautionary and speculative motives → supply of money fixed by the central bank → equilibrium rate where demand for money = supply → diagram → criticism (ignores real factors, indeterminate).

Q5. Explain any two theories of profit.

Outline: risk theory (Hawley: profit is reward for risk-taking) → uncertainty theory (Knight: insurable risks are costs, non-insurable uncertainty earns profit) → innovation theory (Schumpeter: profit from innovations, temporary until imitated) → short criticism of each.

Exam tip

For rent, always separate Ricardian rent (land only) and modern rent (any factor, surplus over transfer earnings). Many students mix the two.