可汗学院的微观经济还没更新完，这次的图像来自 https://www.reviewecon.com/microeconomics-graphs 

可以先想想图内数字的含义再看文字解释（原网站排版更适合电脑/平板端）

1.Inefficient use of resources, but it is possible to produce at this point.

2.Scarcity prevents this level of production without new resources. (trade may also make this point possible).

3 to 4 Increasing opportunity costs if PPC is concave. This is due to resources not being equally adaptable both products. For constant costs the PPC will be a straight line.•Increases in the quality or quantity of resources as well as technological improvements will shift the PPC outward.•Decreases in the quality or quantity of resources will shift the PPC inward.

Single Shifts

•Demand ↑=P ↑ Q ↑: Point 1 to 2•Demand ↓=P ↓ Q ↓: Point 1 to 8•Supply ↑= P↓ Q↑: Point 1 to 6•Supply ↓= P ↑ Q↓:Point 1 to 5Double Shifts•When 1 axis shows an increase then decrease with each shift, that axis is indeterminate.•Demand ↓ Supply ↓P Indeterminate Q ↓:Point 1 to 8 to 7. •Demand ↑ Supply ↑P Indeterminate Q ↑: Point 1 to 2 to 4.•Demand ↑ Supply ↓P ↑ Q Indeterminate: Point 1 to 2 to 3.•Demand ↓  Supply ↑P ↓ Q Indeterminate: Point 1 to 8 to 9

•Consumer surplus is the difference between what consumers are willing to pay (the demand curve) and the price they actually pay.  It is found by taking the price consumers pay from the y axis straight across to the demand curve or the quantity exchanged (which ever is less), then going up until you hit the demand curve.•Producer surplus is the difference between the marginal cost of production and the price. It is found by taking the price producers receive from the y axis straight across to the supply curve or the quantity exchanged (which ever is less), then going down until you hit the supply curve.1.Consumer Surplus2.Producer Surplus1+2= Economic Surplus

1.Triangle is dead weight loss2.Producer surplus3.Consumer Surplus4.There is a surplus of products in the market (Qs>Qd)•The quantity that actually exchanges hands is Qd (there can be more sold than consumers are willing to buy at the current price.

1.Triangle 1 is dead weight loss2.Producer surplus3.Consumer Surplus4.There is a Shortage of products in the market (QsMC) when they are unregulated.**If a monopoly perfectly price discriminates, the MR merges with the DARP and they become allocatively efficient.

1.Productive efficient point(Minimum of ATC)2.Allocative efficient point(MC=MB) quantity below3.Actual output (MR=MC) and price (DARP above MR=MC at point 4)5.Unit elastic portion of the demand curve (where MR equals zero at that quantity).  Demand is inelastic below and elastic above this point.•Dead Weight loss is in the triangle between points 2,3, & 4.•If the firm is making a profit (the ATC is lower than price), firms will enter the market giving each existing firm a smaller share of the market. That shifts DARP and MR to the left.•If the firm is incurring a loss (ATC higher than price), the opposite occurs as firms exit the market.

•Industry – When the supply of labor in the industry decreases (shifting supply to S2) the wage increases and the quantity of workers decreases•Firm – The increase in the wage shifts the firm’s labor supply curve (MRC) upward. As a result, they hire fewer workers (Q2)

•Firm still hires the quantity where MRC=MRP•Pm is the wage all workers are paid and Qm is the number the firm hires.•Pc and Qc is the wage and number of workers hired if this were a competitive market. A monopsony hires fewer worker and pays lower wages than a competitive market.•The MRC is higher than the wage (supply) because the firm must raise the wage for all of their workers when they hire more.•1 and 2 are dead weight loss.

A.The output and price without government intervention. Inefficient because the MSC>MSB due to the externalityABE = Dead weight loss before the tax (no dead weight loss after the tax) created by over productionB.The output and price after the tax. (The tax shifts the supply curve to the left)CBP2P3=Total Tax RevenueP2-P3=The price of the taxCDP1P3=Tax paid by producerBDP1P2= Tax paid by consumer**Here the tax makes the market more efficient and reduces dead weight loss.

B. The output and price without government intervention (inefficient because MSB>MSC)C. The efficient output and price where MSC=MSBABC=the deadweight loss created by under production prior to the subsidy. There is no deadweight loss after the subsidy corrects this market failure.P2-P3=The value of the subsidy.P2P3DC= The total Cost of the Subsidy**Here a tax would increase dead weight loss.

C. Output and price without government intervention.  Inefficient because MSB>MPC.BCE=Deadweight loss created by underproduction. There is no deadweight loss after the subsidySince the subsidy is given to the producer instead, it shifts the supply curve to the right (MPC-Subsidy)Q2. The efficient quantity where MSB equals MSC (No external cost so MSC is MPC).P2 is the price suppliers receive after the subsidy.P3 is the price consumers pay after the subsidy.P2-P3=The value of the subsidyP2P3AB=The Total Cost of the subsidy**Here a tax would increase dead weight loss.

•Lorenz curve – measures the distribution of wealth within a country.•The closer the curve is to the line of equality, the more equal the distribution is.•Gini Ratio= A/(A+B)–Value of zero – Complete equality–Value of one – Complete inequality

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