📚 The Macroeconomy: Core Concepts and Policy Objectives | 宏观经济：核心概念与政策目标
Macroeconomics studies the economy as a whole, focusing on aggregate output, employment, inflation and international trade. For Cambridge A-Level Economics, understanding the macroeconomy requires analysing how total demand and total supply interact, how national income flows through the economy, and how governments use policy to achieve key objectives.
宏观经济学将经济作为一个整体进行研究，重点关注总产出、就业、通货膨胀和国际贸易。在剑桥 A-Level 经济学中，理解宏观经济需要分析总需求与总供给如何相互作用、国民收入如何在经济中流动，以及政府如何运用政策来实现关键目标。
1. The Circular Flow of Income | 收入循环流转
In macroeconomics, the circular flow of income shows how money moves between households and firms. Households provide factors of production such as labour and capital, and firms pay them incomes in the form of wages, rent, interest and profit. Households then use this income to buy goods and services from firms, so the value of output, income and expenditure is identical in a simple closed economy.
在宏观经济学中，收入循环流转展示了货币在家庭和企业之间如何流动。家庭提供劳动和资本等生产要素，企业以工资、租金、利息和利润的形式向家庭支付收入。家庭随后用这些收入购买企业生产的商品和服务，因此在一个简单的封闭经济中，产出、收入和支出的价值是相等的。
A more realistic model includes leakages from the circular flow, namely saving, taxation and imports, and injections such as investment, government spending and exports. Equilibrium national income occurs when total leakages equal total injections, so the level of aggregate demand is stable.
更现实的模型包括从循环流转中漏出的部分，即储蓄、税收和进口，以及投资、政府支出和出口等注入。当总漏出等于总注入时，国民收入达到均衡，总需求水平保持稳定。
2. Aggregate Demand | 总需求
Aggregate demand (AD) is the total planned spending on domestic goods and services at a given price level in a period. Its components are consumption (C), investment (I), government spending (G), and net exports (X − M).
总需求（AD）是在一定时期内，在给定价格水平下对国内商品和服务的计划总支出。其组成部分是消费（C）、投资（I）、政府支出（G）和净出口（X − M）。
AD = C + I + G + (X − M)
The AD curve slopes downward because a lower price level raises the real value of money balances, lowers interest rates and makes domestic goods cheaper relative to imports. Changes in confidence, interest rates, fiscal policy, household wealth, exchange rates and world income shift the AD curve.
总需求曲线向右下方倾斜，因为较低的价格水平会提高实际货币余额、降低利率，并使国内商品相对于进口商品更便宜。消费者信心、利率、财政政策、家庭财富、汇率和世界收入的变化会使总需求曲线移动。
3. Aggregate Supply | 总供给
Aggregate supply is the total output producers are willing and able to supply at each price level. In the short run, the SRAS curve slopes upward because input prices and wages are often sticky, so higher prices improve profit margins. In the long run, the LRAS curve is vertical at potential output, determined by available resources and technology.
总供给是生产者在每个价格水平下愿意并能够提供的总产出。在短期内，短期总供给（SRAS）曲线向上倾斜，因为投入品价格和工资往往具有粘性，较高的价格会提高利润率。在长期，长期总供给（LRAS）曲线在潜在产出处垂直，由可用资源和技术决定。
SRAS shifts when production costs change, for example because of changes in commodity prices, wages, indirect taxes or the exchange rate, and when productivity changes. LRAS shifts when the quantity or quality of factors of production improves, or when technological progress raises productive efficiency.
当生产成本变化时，短期总供给曲线移动，例如大宗商品价格、工资、间接税或汇率变化，以及生产率变化。当生产要素的数量或质量改善，或技术进步提高生产效率时，长期总供给曲线移动。
4. Macroeconomic Equilibrium | 宏观经济均衡
Macroeconomic equilibrium occurs where AD equals SRAS. This determines the actual price level and the level of real GDP in the short run. If AD exceeds SRAS at the potential output level, there is an inflationary gap; if AD is below it, there is a deflationary or recessionary gap.
宏观经济均衡发生在总需求等于短期总供给的地方。这决定了短期的实际价格水平和实际 GDP 水平。如果总需求在潜在产出水平上超过短期总供给，就存在通胀缺口；如果总需求低于潜在产出，就存在通缩缺口或衰退缺口。
An output gap is positive when actual output is above potential, putting upward pressure on prices. A negative output gap means spare capacity and unemployment above the natural rate. Over time, changes in wages and prices may move SRAS and restore long-run equilibrium, but this adjustment can be slow.
当实际产出高于潜在产出时，产出缺口为正，给价格带来上升压力。负产出缺口意味着存在闲置产能，失业率高于自然失业率。随着时间推移，工资和价格的变化可能移动短期总供给并恢复长期均衡，但这种调整可能很缓慢。
5. Economic Growth | 经济增长
Economic growth is an increase in real GDP over time. Actual growth refers to the percentage increase in real output, while potential growth refers to an outward shift of the LRAS curve or an increase in the economy’s productive capacity.
经济增长是实际 GDP 随时间的增加。实际增长指实际产出的百分比增长，而潜在增长指长期总供给曲线的外移或经济生产能力的提高。
Growth can raise living standards, create employment and increase tax revenue, but it may also lead to environmental damage, resource depletion and widening inequality. Sustainable growth requires balancing current output gains with the preservation of resources for future generations.
增长可以提高生活水平、创造就业和增加税收，但也可能导致环境破坏、资源枯竭和贫富差距扩大。可持续增长要求在提高当前产出的同时，为后代保护资源。
6. Unemployment | 失业
Unemployment refers to people who are willing and able to work, actively seeking work, but unable to find a job. The unemployment rate is calculated as the number of unemployed divided by the labour force, multiplied by 100.
失业指愿意并能够工作、正在积极寻找工作但找不到工作的人。失业率用失业人数除以劳动力人数再乘以 100 计算。
Unemployment rate = (Unemployed ÷ Labour force) × 100
Main types of unemployment include frictional unemployment during job search, structural unemployment caused by mismatch of skills, cyclical unemployment caused by weak aggregate demand, and seasonal unemployment. High unemployment reduces incomes, lowers consumption, increases government welfare spending and can cause social costs.
失业的主要类型包括求职过程中的摩擦性失业、技能不匹配导致的结构性失业、总需求疲软导致的周期性失业以及季节性失业。高失业率会减少收入、降低消费、增加政府福利支出并造成社会成本。
7. Inflation and Deflation | 通货膨胀与通货紧缩
Inflation is a sustained rise in the general price level. It is usually measured by the percentage change in a consumer price index (CPI). Deflation is a sustained fall in the general price level.
通货膨胀是总体价格水平的持续上升。通常用消费者价格指数（CPI）的百分比变化来衡量。通货紧缩是总体价格水平的持续下降。
Inflation rate = ((CPI current − CPI previous) ÷ CPI previous) × 100
Demand-pull inflation occurs when AD increases faster than aggregate supply, while cost-push inflation is caused by rising production costs such as energy or wages. Moderate inflation can encourage spending and investment, but high or unpredictable inflation distorts price signals, reduces real incomes and may require contractionary policy. Deflation can be even more damaging because it encourages households to delay spending and increases the real burden of debt.
需求拉动型通货膨胀发生在总需求增长快于总供给时，而成本推动型通货膨胀由能源或工资等生产成本上升引起。适度的通胀可以鼓励消费和投资，但高通胀或不可预测的通胀会扭曲价格信号、降低实际收入，并可能需要紧缩政策。通货紧缩可能更具破坏性，因为它鼓励家庭推迟支出并增加实际债务负担。
8. Balance of Payments | 国际收支
The balance of payments records all economic transactions between residents of a country and the rest of the world. The current account includes trade in goods, trade in services, primary income such as profits and interest, and secondary income such as transfers.
国际收支记录了一国居民与世界其他地区之间的所有经济交易。经常账户包括货物贸易、服务贸易、利润和利息等初级收入以及转移支付等次级收入。
A current account deficit means a country spends more on imports and investment income than it earns from exports and inflows. This may be financed by financial account inflows or by running down reserves. Persistent deficits can indicate a loss of competitiveness, while large surpluses may reflect excessive saving relative to investment.
经常账户赤字意味着一国在进口和投资收益上的支出超过从出口和流入中获得的收入。这可以通过金融账户流入或减少储备来融资。持续的赤字可能表明竞争力下降，而巨额顺差可能反映储蓄相对于投资过多。
9. Exchange Rates | 汇率
An exchange rate is the price of one currency in terms of another. Appreciation means the currency becomes stronger, so imports are cheaper and exports more expensive. Depreciation means the currency becomes weaker, making exports cheaper and imports dearer.
汇率是一种货币以另一种货币表示的价格。升值意味着货币走强，进口更便宜，出口更贵。贬值意味着货币走弱，出口更便宜，进口更贵。
Exchange rates are determined by demand and supply for currencies, influenced by interest rates, inflation differentials, speculation, trade flows and political stability. A depreciation can improve the trade balance in the long run if the Marshall-Lerner condition holds, but it also raises import prices and may add to inflation.
汇率由货币的供求决定，受利率、通胀差异、投机、贸易流动和政治稳定影响。如果满足马歇尔-勒纳条件，本币贬值长期可改善贸易收支，但也会提高进口价格并可能加剧通货膨胀。
10. Macroeconomic Policy Objectives and Instruments | 宏观经济政策目标与工具
Governments typically pursue several macroeconomic objectives: low and stable inflation, low unemployment, sustainable economic growth, a satisfactory balance of payments position, and a more equal distribution of income and wealth. These objectives can conflict, for example low unemployment may raise demand and cause inflation, while rapid growth may worsen the current account.
政府通常追求几个宏观经济目标：低而稳定的通胀、低失业、可持续的经济增长、满意的国际收支状况以及更公平的收入和财富分配。这些目标之间可能发生冲突，例如低失业可能提高总需求并引发通胀，而快速增长可能使经常账户恶化。
Policy instruments include fiscal policy, which changes government spending and taxation; monetary policy, which adjusts interest rates and the money supply; supply-side policies, which improve productivity and the productive capacity of the economy; and exchange rate policy. The choice of instruments depends on the nature of the shock and the trade-offs policymakers are willing to accept.
政策工具包括改变政府支出和税收的财政政策、调整利率和货币供应量的货币政策、提高生产率和经济生产能力的供给侧政策以及汇率政策。工具的选择取决于冲击的性质以及政策制定者愿意接受的取舍。
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