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International Economics. New trade theory. New trade: Key elements, IRS & IC. IRS Internal to firm (i.e. firm sees its AC fall with its output) External to firm (i.e. firm sees its AC fall with industry output, but believes its AC are constant w.r.t. its own output, i.e. it is atomistic).

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## International Economics

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**International Economics**New trade theory**New trade: Key elements, IRS & IC**• IRS • Internal to firm (i.e. firm sees its AC fall with its output) • External to firm (i.e. firm sees its AC fall with industry output, but believes its AC are constant w.r.t. its own output, i.e. it is atomistic) Firm-level output (internal IRS) Sector-level output (external IRS)**New trade theory: Other key element is Imperfect Competition**(IC). • External IRS can be done with PC. • Internal IRS requires consideration of IC • IRS means AC>MC • P=MC<AC means losses, so need P>MC to have non negative profits. • P>MC means IC • Need to have a refresher on IC …**Monopoly background**Thus MR curve is always below the demand curve and typically steeper • What is Marg’l Rev? • MR = Price – Q times (change in P) Marginal Revenue Curve Price Price Demand Curve Marginal Cost Curve Demand Curve P* P’ A P” B D Marginal Cost C E Q* Q’ Sales Q’+1 Sales**Monopoly**Price, p MC pMC AC Demand MR, Marginal Revenue qMC Quantity, q**Monopolistic competition background**• Monopolistic competition is when firms compete with each other indirectly since each firm produces a different variety of the good, say cars, electric motors, chemicals, etc. • Each firm takes prices of other firms as given and thus views itself as having a monopoly on the “residual demand”, i.e. the demand that is leftover after the sales of the other firms are taken account of. • As more firms enter the market, 2 things happen: • Residual demand curve shifts in for each firm (newcomer’s sales reduce demand left for others). • Always • The Residual demand curves become flatter since the varieties are now closer substitutes (i.e. since there are more ‘nearby’ varieties, the demand for any single variety is more responsive to price changes of other varieties). • Often, i.e. not for all goods.**Price**RD • Graphically, new entrants mean both RD (resid.demand) and MR curve shift down and get flatter. • This makes each firm lower its price-MC markup, so prices fall. P* P’ RD’ MC MR MR’ Q’ Q* Sales**Individual demand curves**• total demand for industry's output (S) Q • own price (P) Q • prices charged by rivals (P’) Q • number of firms in industry (n) Q demand: Q = S [1/n - b(P - P’)] (b = 30,000 how many firms (n) ? what price do they charge (P) ?**PP-CC diagram**• In the book, Krugman uses maths to make these basic points about IC & IRS. • You can skip the math and just read it for ideas • Rely on the previous diagram to motivate why more firms leads to lower prices – this is, after all, a very intuitive outcome (more competition, lower prices).**CC curve**• It shows how many firms can ‘break even’, i.e. earn zero profits for any given number of firms. • The sales of each firm falls as n rises, so firms would need a higher price to breakeven as the number of firms rises. • Do examples. • Plainly there is a tension between the CC and PP; CC is what price they’d need to breakeven, PP is the price that normal competition would lead them to charge. • Where PP & CC met, firms are charging profit-max prices (MR=MC) AND they are breaking even (P=AC).**number of firms and average cost**• Firm’s costs: C = F + cQC = 750,000,000 + (5000Q) AC = F/Q + cAC = (750,000,000/Q) + 5000 (internal economies of scale) MC = C/Q = c • Firm’s market share: Q = S/nS = 900,000 AC = nF/S + cAC =833n +5,000 nAC (CC-schedule)**PP curve**• We plot the more-competition-lower-prices relationship as PP. • It is enough to understand roughly the logic that more firms in the market would result in a lower price. • More detailed understanding, via monopolistic competition model is a plus.**2. number of firms and price**• n competition P P = c + 1/(bn) P = 5000 + 1/(30,000n) (PP-schedule) • (can be formally derived from profit maximization: MR = MC)**PP-CC diagram**BE COMP Next we motivate the CC curve.**Auk’y equilibrium**• In auk’y the nation’s CC is CC1 and the eq’m is where the price of a typical variety is P1 and there are n1 firms. auky**3. equilibrium number of firms**• neq where CCPP n = 6 • Why? n > neqAC > P n (exit) n < neqAC < P n (entry)**Effects of a larger market**• S(e.g., EU's Single Market, 1993) slope of CC economies of scale n product variety P, AC price, cost • intra-industry trade • exchange of goods produced by same industry • about 25% of world trade**Auk’y to FT shift**• If we have FT between 2 identical nations, the CC shifts out to CC2. • With double the market, more firms can breakeven at the same price • In fact 2n1 firms could break even, if there were no change in price • i.e. P1 stays 2n1**Auk’y to FT shift**• But the extra firms also mean more competition, so new FT eq’m is at point 2. • NB: The number of varieties available in each nation has risen from n1 to n2 • n2 <2*n1 but … • So some firms have exited and/or merged and/or bankrupt. • Price of all varieties is lower.**Story**• Auky to FT means bigger mkt but more competition. • The extra competition pushes down prices, initially to a point where firms are losing money. • Then ‘industry restructuring until profits are restored at 2. p=AC MR=MC 2n1**How can P fall & zero profits?**• The presence of internal IRS is the key to the price fall. • Each of the n2 firms sells more than they in auk’y. • Thus they have lower AC and so can charge a lower price and still breakeven. • NB: zero profits mean P=AC. P” Firm-level output x”**Extreme case; monopolist at home, perfectly competitive**abroad. Pdom set from MR=MC. Pfor set from p=MC.**Less extreme case: price discriminating oligopolist**1. Assume Price-discriminating oligopolist with constant MC across markets. 2. Will determine price/quantity in each market as MC =MR1 = MR2. 3. Result will be different prices in each market depending on market shares Smaller market share means flatter residual demand curve Why? Cost, C and Price, P Cost, C and Price, P Dfor is lower and flatter since firm has smaller market share in foreign mkt. P1 P2 MC MC D2 D1 MR2 MR1 Q1 Quantity, Q Q2 Quantity, Q Market 1 (HOME) Market 2 (export mkt)

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