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AP 各学科「速成」笔记导览

Unit 1: Basic Economic Concept

Opportunity Cost

• \(\text{Opportunity Cost} = \frac{\text{forgone}}{\text{gain}}\)

• Possibility Production Frontier

  

Shift of OC

• Point Shift
  • Inside the Frontier
    • Input resources do not be allocated efficiently
      • Unemployment
  • On the Frontier
    • Resources have been allocated efficiently
  • Outside the Frontier
    • We can comsume by importing goods
    • Impossible
• Curve shift
  • X Tech increase → X Border shift outward
• No effect
  • Demand of product
  • Price of product
  • Other factor that don’t do with allocating efficiency

Shape of OC

• Bowed outward / convex

  • Increasing OC

  

• Bowed in / concave

  • Decreasing OC

  

• Straight Line

  • Constant OC
  • Resources are completely adaptable to alternative uses

  

• AP Classroom

  

Absolute Advantages

• Someone using same input could absolutely gain greater amount of some product than others.

• Someone using same input could relatively / comparatively have lower opportunity cost than others.

• Comparative Advantage
  • Milk: Martin
  • Pizza: Edward
• Input question: \(N\) hours → produce \(1\) unit
• Output question: \(24\text{(or arbitrary fixed hours)}\) -> \(N\) unit
• Generally, we transform the input question to output question through a fixed input hours. (e.g \(24\) hours)

Trade Price

• If countries trade based on the opportunity cost, country A would uses one unit product A to exchange a range amount of product B between country A OC of product A to country B OC of product A.

Untitled

• Price of product A will be a range between \(2 \sim 3\)

Utility

• Maximizing Utility Formula

\[\frac{\text{MU}_x}{\text{P}_x} = \frac{\text{MU}_y}{\text{P}_y}\]

• Double income, price
  • No effect

Unit 2: Supply and Demand

Elasticity

General Formula

\[\text{Elasticity} = \frac{\Delta\text{Quantity}\%}{\Delta\text{Price}\%}\]

Change rate (Take \(\Delta Q\) as an example)

• Divide original amount of quantity

  • A to B

  \[\Delta \text{Quantity}\% = \frac{Q_B - Q_A}{Q_A} \]

  • B to A

  \[\Delta \text{Quantity}\% = \frac{Q_A - Q_B}{Q_B}\]

• Mid-point

\[\Delta \text{Quantity}\% = \frac{Q_A - Q_B}{\frac{Q_A + Q_B}{2}}\]

Elasticity of Curve

• tend to be even / horizontal curve
  • more elasticity

• tend to be steep / vertical curve
  • more inelasticity

TR & Elasticity

• As shown in the following figure: Firms usually operate in \(\text{Elasticity} > 0\) since \(MR > 0\), \(TR\) is continuously increasing.

Income Elasticity of Demand (IED)

\[\text{IED} = \frac{\Delta\text{Quantity}\%}{\Delta \text{Income}\%}\]

• \(\text{IED} > 0\), which means \(\Delta Q,\;\Delta I\) changing toward same direction. Normal Good (+)
• \(\text{IED} < 0\), which means \(\Delta Q,\;\Delta I\) changing toward opposite direction. Inferior Good (-

Cross-price Elasticity of Demand (XED)

\[\text{XED} = \frac{\Delta\text{Quantity}_X\%}{\Delta \text{Price}_Y\%}\]

• \(\text{XED} > 0\), which means \(\Delta Q_X,\;\Delta P_Y\) changing toward same direction. Substitutes (+)
• \(\text{XED} < 0\), which means \(\Delta Q_X.\;\Delta P_Y\) changing toward opposite direction. Complement (-)

Efficiency

Allocated Efficiency

• Maximize the Total Surplus, \(\text{S = D}\)
• Example
  • Market equilibrium
  • Supply = Demand
  • Perfectly Competitive Market MC (Supply) = MR (Demand)

Production Efficiency

• Production Efficiency is Minimize the Production Cost
• Example:
  • ATC intersects MC

Tax

Per-unit Tax

• Per-unit Tax: Size of Tax
• For Example:
  • Per-unit Tax is \(\$3.30 - \$2.80 = \$0.5\)

Tax and Elasticity

• Which curve is more elastic, the less tax they need to pay.

Deadweight Loss

• The surplus that consumer surplus and producer surplus could not reach.

\[\text{Deadweight Loss} = \text{Total Surplus} - (\text{Comsumer Surplus} + \text{Producer Surplus})\]

• Government Action

  • Price Ceiling

  

  • Price Floor

  

  • Tax

  

  • Tariff

  

  • Subsidy

  

• Monopoly