分清楚整条曲线的移动，和一个点在曲线上移动而曲线不动。
除了价格、需求量之外的其他因素变化，会导致曲线的移动。如天气热导致多卖冰激凌，糖涨价导致冰激凌成本提高等，会引发曲线的移动
新的供应商加入，竞争激烈导致价格下降，会引起需求曲线上点的移动。
demand curve and supply cures intersect at a point, which we call it equilibrium point.
when some events happen, we analyze the affect with three steps.
1. analyze which curve shifts
2. decide whether the curve moves to the left or right
3. a new equilibrium formed. study this new point and address what happened.
complements: related goods of which demand changes while the goods under analyze changes
substitutes: a good by which we can replace the goods under analyze.
Use consumer surplus and producer surplus to measure the benefit of economy---a method of measuring the total welfare of the trade.
tax is a wedge put between the demand and supply curves.
taxation shrinks the total market size. tax burden is distributed to sellers and buyers by the force of demand and supply curves. the side of which has more elasticity shares less burden, the other side shares more. This burden share has nothing to do with how the taxation is levied.
For a typical worker, if all forms of labor taxes are added together, the marginal tax rate on labor income—the tax on the last dollar of earnings—is about 40 percent.
Taxation induces a deadweight cost, which represents the shrink of the market. traders are taxed, so the market size becomes smaller, thus this part does not contribute to the revenue of tax.
Chapter 13:
diminishing marginal product(边际产量递减）：the cost of unit production rises when production amout rises.
fix cost: rent, wage, machines etc
variable cost: the more production, the higher cost
average cost:total cost/ number of production
marginal cost(边际成本): Marginal cost = Change in total cost/Change in quantity. MC = ΔTC/ΔQ
minimum average total cost plays a key role in the analysis of competitive firms.
the intersection of MC and ATC is the minimum ATC.
key mind of Chap 13: the relation of quantity of oupput produced and the cost(mainly avc,mc)
Final result of a Competitive Market: Ecnomic profit is zero, with opptunity cost taken into consideration. Good firms may have ecnomic profit, weak firms may have negative ecnomic profit even negative accountant profit.
Chapter 15: Monopolies.
Three types of monopoly:
1, the firm monoply a natrual resource. This kind of monopoly is rare because natrual resouces now are golbal configured.
2, Govenment created monopoly, like highway company with a highway permission, or patent, copyright.
3, natrual monopoly. the market has a specific character under which the firm's average total cost falls as the quantity of production output rises. examples are water supply company, electric company etc. they must build a large network frastructure with a very high fixed cost. after this is done, the marginal cost is very low.
the following rules are true for both competitive market and monopolized market: the profit maximization point is the point at which marginal revenue equals marginal cost.
Question to be study: why is the intersection of MC and ATC "efficient scale"? the answer is on page 304(pdf page).
Labor, land and capital.
In equilibrium, each factor of production earns the value of its marginal contribution to the production of goods and services.
Chapter 19-20 income distribution. mainly about how income is distributed, ecnomic equality and how the govenment combat poverty. Measurement of equality is difficult for some reasons and such difficulty makes policy making also difficut. Policymakers also face trade offs between benefit the poor and disencourage the incentive to work.
chapter 21: theory of consumer choice. This theory is a very useful thinking model. see the conculusion section.
GDP=COMSUMPTION+INVESTMENT+NET_EXPORT+GOVENMENT_PURCHASE
for a closed economy, net export is 0, so GDP(denoted as Y), Y=C+I+G
national saving =Y - G - C, so national saving is equal to Investment
private saving = Y-T(TAX)-C
public saving = T-G
national saving=private saving+public saving = Y-T-C+T-G=Y-C-G
national bond is issues at a fix interest rate, with a variable par value（票面价值）
when Interest Rate(ir) rises, the real interest rate of national bond would rise. However, since the nominal interest rate is fixed, the par value has to fall to make the real interest rate to rise. That is why interest rate rise causes the bond price to fall.
U.S. national bond is called Treasury bonds. 10年期美国国债是全球资产价格的锚。美债收益率走高，则各类资产的收益率也要走高，那么资产的价格就要下降。
2 ways to increase investment: reduce private saving tax or reduce govenment deficit. The reason why reduce deficit can increase investment? govenment pay debt, so banks or private people have more fund
美国如何“割羊毛”？