📚 Year 11 CAIE Economics: Formula & Theorem Quick Reference Handbook | CAIE经济：公式定理速查手册
This handbook compiles every essential formula, key economic law, and critical graphical relationship prescribed in the Year 11 CAIE Economics syllabus. It is designed as a rapid revision companion, enabling you to recall quantitative and theoretical foundations accurately and efficiently before your examinations.
本手册汇集了 Year 11 CAIE 经济课程大纲规定的所有重要公式、关键经济定律和核心图形关系。它旨在作为快速复习伴侣，帮助你在考试前准确高效地回忆起定量和理论基础。
1. Basic Economic Concepts and Opportunity Cost | 基本经济概念与机会成本
The economic problem arises from scarcity: finite resources cannot satisfy infinite human wants. Every choice involves an opportunity cost, which is the value of the next best alternative forgone.
经济问题源于稀缺性：有限的资源无法满足无限的人类欲望。每一个选择都涉及机会成本，即所放弃的次优替代品的价值。
Opportunity Cost = Value of Next Best Alternative Sacrificed
机会成本 = 放弃的次优选择的价值
The Production Possibility Curve (PPC) illustrates maximum output combinations of two goods when all resources are used efficiently. Points inside the PPC represent unemployment of resources, while outward shifts indicate economic growth.
生产可能性曲线（PPC）展示了当所有资源被有效利用时两种商品的最大产出组合。曲线内的点表示资源未充分利用，而向外移动则表示经济增长。
2. Demand, Supply and Market Equilibrium | 需求、供给与市场均衡
The law of demand states that as price falls, quantity demanded rises, ceteris paribus. The law of supply states that as price rises, quantity supplied increases, ceteris paribus.
需求定律指出，其他条件不变，价格下降时需求量上升。供给定律指出，其他条件不变，价格上升时供给量增加。
Market Equilibrium: Qd = Qs
市场均衡：需求量 = 供给量
A shift of the demand curve is caused by changes in non-price determinants such as income, tastes, prices of related goods, expectations and population. A shift of the supply curve results from changes in production cost, technology, taxes, subsidies and number of sellers.
需求曲线的移动由非价格决定因素引起，如收入、偏好、相关商品价格、预期和人口。供给曲线的移动源于生产成本、技术、税收、补贴和卖家数量的变化。
3. Elasticity: Price, Income and Cross Elasticities | 弹性：价格弹性、收入弹性和交叉弹性
Price elasticity of demand (PED) measures the responsiveness of quantity demanded to a change in the good’s own price.
需求价格弹性（PED）衡量需求量对商品自身价格变化的反应程度。
PED = %ΔQd ÷ %ΔP
PED = 需求量变动的百分比 ÷ 价格变动的百分比
If |PED| > 1, demand is elastic; if |PED| < 1, demand is inelastic; if |PED| = 1, demand is unit elastic. Perfectly elastic demand has |PED| = ∞ and a horizontal demand curve; perfectly inelastic demand has |PED| = 0 and a vertical demand curve.
若 |PED| > 1，需求富有弹性；若 |PED| < 1，需求缺乏弹性；若 |PED| = 1，需求为单位弹性。完全弹性需求时 |PED| = ∞，需求曲线水平；完全无弹性需求时 |PED| = 0，需求曲线垂直。
Income elasticity of demand (YED) shows how demand changes as consumer income changes. Cross elasticity of demand (XED) shows how demand for one good responds to a price change in another good.
需求收入弹性（YED）显示需求如何随消费者收入变化。需求交叉弹性（XED）显示一种商品的需求对另一种商品价格变化的反应。
YED = %ΔQd ÷ %ΔY
YED = 需求量变动的百分比 ÷ 收入变动的百分比
XED = %ΔQd(A) ÷ %ΔP(B)
XED = 商品A需求量变动的百分比 ÷ 商品B价格变动的百分比
YED > 0 indicates a normal good; YED < 0 indicates an inferior good. XED > 0 implies substitutes; XED < 0 implies complements.
YED > 0 表明是正常品；YED < 0 表明是低档品。XED > 0 意味着替代品；XED < 0 意味着互补品。
4. Price Elasticity of Supply (PES) | 供给价格弹性
Price elasticity of supply (PES) measures the responsiveness of quantity supplied to a change in price.
供给价格弹性（PES）衡量供给量对价格变化的反应程度。
PES = %ΔQs ÷ %ΔP
PES = 供给量变动的百分比 ÷ 价格变动的百分比
PES > 1 indicates elastic supply; PES < 1 indicates inelastic supply. Determinants of PES include production time lag, spare capacity, availability of raw materials and ease of storage.
PES > 1 表示供给富有弹性；PES < 1 表示供给缺乏弹性。PES 的决定因素包括生产时滞、闲置产能、原材料的可得性和储存的难易程度。
5. Costs of Production | 生产成本
In the short run, at least one factor of production is fixed. Total cost (TC) comprises total fixed cost (TFC) and total variable cost (TVC). Average costs and marginal cost are derived as follows.
在短期内，至少有一种生产要素是固定的。总成本（TC）包括总固定成本（TFC）和总可变成本（TVC）。平均成本和边际成本可由以下公式得出。
TC = TFC + TVC
总成本 = 总固定成本 + 总可变成本
AFC = TFC ÷ Q
平均固定成本 = 总固定成本 ÷ 产量
AVC = TVC ÷ Q
平均可变成本 = 总可变成本 ÷ 产量
AC = AFC + AVC or TC ÷ Q
平均总成本 = 平均固定成本 + 平均可变成本 或 总成本 ÷ 产量
MC = ΔTC ÷ ΔQ
边际成本 = 总成本变动量 ÷ 产量变动量
The law of diminishing returns states that as more units of a variable factor are added to a fixed factor, the marginal product will eventually fall. This causes the MC curve to eventually rise.
边际收益递减定律指出，在固定生产要素上不断增加可变要素，边际产量最终会下降。这导致边际成本曲线最终上升。
6. Revenue, Profit and Objectives of Firms | 收入、利润与企业目标
A firm’s total revenue, average revenue and marginal revenue are linked directly to price and output decisions.
企业的总收入、平均收入和边际收入与价格和产出决策直接相关。
TR = P × Q
总收入 = 价格 × 销售量
AR = TR ÷ Q = P
平均收入 = 总收入 ÷ 销售量 = 价格
MR = ΔTR ÷ ΔQ
边际收入 = 总收入变动量 ÷ 销售量变动量
Profit = TR − TC
利润 = 总收入 − 总成本
Firms may pursue profit maximisation where MC = MR, or alternative objectives such as sales maximisation (TR maximised, MR = 0) or satisficing.
企业可能追求利润最大化，此时边际成本等于边际收入（MC = MR），也可能追求其他目标，如销售额最大化（总收入最大，边际收入为零）或满意化。
7. Market Structures and Efficiency | 市场结构与效率
Perfect competition features many buyers and sellers, homogeneous products, free entry and exit, and perfect information. In such a market, firms are price takers, and allocative and productive efficiency are achieved in the long run (P = MC and P = minimum AC).
完全竞争的特征是大量买者和卖者、同质产品、自由进入和退出以及完全信息。在这种市场中，企业是价格接受者，长期中实现配置效率和生产效率（价格 = 边际成本，且价格 = 最低平均成本）。
Monopoly exists when a single firm dominates the market with high barriers to entry. A monopolist is a price maker and can earn supernormal profit in the long run. It may produce at a point where P > MC, causing allocative inefficiency.
垄断是指单一企业主导市场且进入壁垒很高。垄断者是价格制定者，长期可获得超额利润，其生产点通常价格高于边际成本，导致配置无效率。
| Market Structure | No. of Firms | Product Differentiation | Barriers to Entry |
|---|---|---|---|
| Perfect Competition | Very many | Homogeneous | None |
| Monopolistic Competition | Many | Differentiated | Low |
| Oligopoly | Few dominant firms | Often differentiated | High |
| Monopoly | One | Unique | Very high |
市场结构特征速查
8. Aggregate Demand and Aggregate Supply | 总需求与总供给
Aggregate demand (AD) is the total spending on an economy’s goods and services at a given price level. It is measured by the expenditure method.
总需求（AD）是在给定价格水平下对一国商品和服务的总支出。它通过支出法衡量。
AD = C + I + G + (X − M)
总需求 = 消费 + 投资 + 政府支出 + (出口 − 进口)
Aggregate supply (AS) is the total output of goods and services that firms are willing and able to produce at each price level. In the short run, the AS curve is upward-sloping; in the long run, it may be vertical at the full-employment level of output.
总供给（AS）是企业在不同价格水平上愿意且能够生产的商品和服务的总产出。短期总供给曲线向右上方倾斜；长期总供给曲线可能在全就业产出水平呈垂直状态。
9. Macroeconomic Objectives and Indicators | 宏观经济目标与指标
Governments aim for economic growth, low unemployment, price stability and a stable balance of payments. Key indicators help measure performance against these goals.
政府追求经济增长、低失业率、物价稳定和国际收支平衡。关键指标有助于衡量这些目标的表现。
Unemployment Rate = (Number of Unemployed ÷ Labour Force) × 100
失业率 = (失业人数 ÷ 劳动力) × 100
Inflation Rate = [(CPIcurrent − CPIprevious) ÷ CPIprevious] × 100
通货膨胀率 = [(当期CPI − 上期CPI) ÷ 上期CPI] × 100
Economic Growth Rate = [(Real GDPcurrent − Real GDPprevious) ÷ Real GDPprevious] × 100
经济增长率 = [(当期实际GDP − 上期实际GDP) ÷ 上期实际GDP] × 100
The balance of payments current account records trade in goods, services, primary income and secondary income. A deficit means debits exceed credits, while a surplus means credits exceed debits.
国际收支经常账户记录货物、服务、初次收入和二次收入的交易。逆差意味着借方大于贷方，顺差意味着贷方大于借方。
10. Fiscal, Monetary and Supply-Side Policies | 财政、货币与供给侧政策
Fiscal policy involves government spending and taxation to influence aggregate demand. The budget balance is the difference between government revenue and expenditure.
财政政策通过政府支出和税收影响总需求。预算余额是政府收入与支出之间的差额。
Budget Balance = Government Revenue − Government Expenditure
预算余额 = 政府收入 − 政府支出
Monetary policy uses changes in interest rates, money supply and exchange rates to control inflation and stabilise the economy. A lower interest rate tends to increase consumption and investment, shifting AD to the right.
货币政策通过调整利率、货币供给和汇率来抑制通胀并稳定经济。降低利率往往会增加消费和投资，使总需求曲线右移。
Supply-side policies aim to increase the productive capacity of the economy, shifting the long-run aggregate supply (LRAS) to the right. Examples include improving education, reducing regulation and investing in infrastructure.
供给侧政策旨在提高经济的生产能力，使长期总供给曲线右移。例子包括改善教育、减少监管和投资基础设施。
11. International Trade and Exchange Rates | 国际贸易与汇率
The terms of trade measure the relative price of exports compared to imports. An improvement means a country can buy more imports for a given quantity of exports.
贸易条件衡量出口相对于进口的价格。贸易条件改善意味着一定数量的出口可以购买更多的进口。
Terms of Trade = (Index of Export Prices ÷ Index of Import Prices) × 100
贸易条件 = (出口价格指数 ÷ 进口价格指数) × 100
Exchange rates can be floating (determined by market forces) or fixed (set by the government). A depreciation of a currency lowers export prices in foreign currency and raises import prices, improving the trade balance if the Marshall-Lerner condition holds.
汇率可以是浮动的（由市场力量决定）或固定的（由政府设定）。货币贬值会降低以外币计算的出口价格并提高进口价格，如果满足马歇尔-勒纳条件，则改善贸易收支。
Marshall-Lerner Condition: |PEDexports| + |PEDimports| > 1
马歇尔-勒纳条件：出口需求价格弹性绝对值 + 进口需求价格弹性绝对值 > 1
12. Economic Growth and Development | 经济增长与发展
Economic growth is measured by an increase in real GDP over time. Real GDP per capita accounts for population changes and provides a rough indicator of living standards.
经济增长以实际GDP随时间的增长来衡量。人均实际GDP考虑了人口变化，提供了一个粗略的生活水平指标。
Real GDP per Capita = Real GDP ÷ Population
人均实际GDP = 实际GDP ÷ 人口
Economic development is a broader concept that includes improvements in health, education, income distribution and environmental quality. The Human Development Index (HDI) combines life expectancy, education and GNI per capita to rank countries.
经济发展是一个更广泛的概念，包括健康、教育、收入分配和环境质量的改善。人类发展指数（HDI）结合了预期寿命、教育和人均国民总收入对国家进行排名。
Sustainable development meets the needs of the present without compromising the ability of future generations to meet their own needs. This requires balancing economic, social and environmental objectives.
可持续发展既满足当代人的需要，又不损害后代人满足其自身需要的能力。这需要平衡经济、社会和环境目标。
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