📚 The Relationship between Unemployment and Inflation | 失业与通货膨胀之间的关系
Unemployment and inflation are the two central indicators of macroeconomic performance. For an A-Level economist, their relationship is not a simple one: sometimes the two variables move in opposite directions, sometimes together, and sometimes the apparent link disappears altogether. Understanding the Phillips curve and its modern refinements is essential for evaluating macroeconomic policy choices.
失业和通货膨胀是衡量宏观经济表现的两个核心指标。对于 A-Level 经济学学习者来说，二者之间的关系并不简单：有时它们朝相反方向变动，有时同向变动，有时表面的联系会完全消失。理解菲利普斯曲线及其现代发展，对于评估宏观经济政策选择至关重要。
This article builds the argument in stages, starting from how the two variables are measured, moving through the short-run trade-off, the natural rate hypothesis, expectations, supply shocks, the quantity theory of money and hysteresis, and finishing with policy implications and exam technique. Each stage adds one layer of sophistication to the same central question: is there a stable trade-off between unemployment and inflation?
本文将分阶段展开论证：先看两个变量如何衡量，再依次讨论短期取舍关系、自然失业率假说、预期、供给冲击、货币数量论与滞后效应，最后落到政策含义与考试技巧。每一阶段都为同一个核心问题增加一层深度：失业与通胀之间是否存在稳定的取舍关系？
1. Two Key Macroeconomic Objectives | 两个关键的宏观经济目标
Governments typically pursue low unemployment and low inflation as major policy objectives. Low unemployment means that scarce labour resources are fully utilised, human capital is maintained, and output is closer to the production possibility frontier. Low inflation protects real incomes, reduces uncertainty, and supports business confidence and long-term investment.
政府通常将低失业和低通胀作为主要的政策目标。低失业意味着稀缺的劳动力资源得到充分利用，人力资本得以维持，产出更接近生产可能性边界。低通胀则保护实际收入、降低不确定性，并支持企业信心与长期投资。
However, these two objectives may conflict, especially in the short run. If the government expands aggregate demand to reduce unemployment, firms facing tighter labour markets may raise wages and pass higher costs on to consumers, pushing inflation up. This possible conflict is the foundation of the Phillips curve debate. If a trade-off exists, achieving one objective may require sacrificing the other. If no stable trade-off exists, policymakers must focus on supply-side improvements and credible nominal anchors instead.
然而，这两个目标可能相互冲突，尤其是在短期内。如果政府扩张总需求以降低失业，面对劳动力市场趋紧的企业可能提高工资，并把更高的成本转嫁给消费者，从而推高通胀。这种可能存在的冲突正是菲利普斯曲线争论的基础。如果取舍关系存在，那么实现一个目标可能需要牺牲另一个目标；如果不存在稳定的取舍关系，政策制定者就必须转而关注供给侧改善和可信的名义锚。
The standard macroeconomic objectives usually include the following:
标准的宏观经济目标通常包括以下几项：
- Low and stable inflation, often around a 2% target | 低而稳定的通胀，通常围绕 2% 的目标
- Low unemployment and high employment | 低失业率与高就业率
- Sustained economic growth | 持续的经济增长
- A satisfactory balance of payments | 令人满意的国际收支状况
- Stable public finances | 稳健的公共财政
2. Measuring Unemployment and Inflation | 失业与通胀的衡量
Unemployment is usually measured by the claimant count, which records people receiving unemployment-related benefits, or by the ILO labour force survey, which counts people actively seeking work but not currently in employment. The claimant count is cheaper and quicker but excludes those who are ineligible for benefits; the ILO measure is internationally comparable and broader, but it is subject to sampling error.
失业通常通过申请失业救济人数来衡量，即记录领取失业相关救济金的人数；或者通过国际劳工组织劳动力调查来衡量，即统计正在积极寻找工作但尚未就业的人数。申请救济人数统计成本更低、速度更快，但会排除那些不符合领取资格的人；ILO 口径具有国际可比性且覆盖更广，但存在抽样误差。
Inflation is measured by changes in the consumer price index (CPI), and sometimes by the retail price index (RPI) or the GDP deflator. CPI uses a weighted basket of goods and services and is used for inflation targeting; RPI includes housing costs such as mortgage interest payments and council tax, which is why it often differs from CPI; the GDP deflator covers all domestically produced output and is the broadest measure of price change.
通胀通过消费者价格指数（CPI）的变化来衡量，有时也用零售价格指数（RPI）或 GDP 平减指数。CPI 使用加权的一篮子商品与服务，是通胀目标制的依据；RPI 包含住房成本，如按揭利息支付和市政税，因此常与 CPI 出现差异；GDP 平减指数覆盖国内生产的全部产出，是范围最广的价格变动衡量指标。
| Measure | 指标 | What it captures | 衡量内容 | Main limitation | 主要局限 |
|---|---|---|
| Claimant count | People claiming unemployment benefits | Excludes ineligible and discouraged workers |
| ILO labour force survey | People actively seeking work | Sampling error; costly to collect |
| CPI | Consumer basket, target measure | Excludes housing costs; basket may be unrepresentative |
| RPI | Includes mortgage interest and council tax | Not an internationally standard measure |
| GDP deflator | All domestically produced output | Not timely; not a consumer cost measure |
A key exam point is that all of these are imperfect measures, so measured unemployment and measured inflation can both overstate or understate the true values. This matters because policy is set on the basis of the statistics, not the underlying reality.
一个关键的考试要点是：这些指标都不完美，因此统计到的失业率和通胀率都可能高估或低估真实值。这一点很重要，因为政策是基于统计数据而非底层现实来制定的。
3. The Short-Run Phillips Curve: The Trade-Off | 短期菲利普斯曲线：取舍关系
In 1958, A. W. Phillips published evidence of a stable inverse relationship between unemployment and the rate of change of money wages in the United Kingdom between 1861 and 1957. Later work replaced wage inflation with price inflation and produced the short-run Phillips curve (SRPC): as unemployment falls, inflation rises, and vice versa.
1958 年，A. W. Phillips 发表证据，显示 1861 至 1957 年间英国失业率与货币工资变动率之间存在稳定的反向关系。后续研究将工资通胀替换为价格通胀，从而得出了短期菲利普斯曲线（SRPC）：失业率下降时通胀上升，反之亦然。
In modern form, the short-run Phillips curve is often written as:
在现代形式中，短期菲利普斯曲线通常写作：
π = πᵉ − β(u − uₙ) + ε
Here π is actual inflation, πᵉ is expected inflation, u is actual unemployment, uₙ is the natural rate of unemployment, β is a positive parameter showing how strongly unemployment gaps translate into inflation, and ε is a supply shock term. The equation shows that the SRPC is drawn for a given level of expected inflation: when πᵉ changes, the whole curve shifts.
其中，π 是实际通胀率，πᵉ 是预期通胀率，u 是实际失业率，uₙ 是自然失业率，β 是正参数，表示失业缺口转化为通胀的强度，ε 是供给冲击项。该方程表明，短期菲利普斯曲线是在给定预期通胀水平下绘制的：当 πᵉ 变化时，整条曲线发生移动。
Two distinct movements must be distinguished:
必须区分两种不同的变动：
- A movement along the SRPC is caused by a change in aggregate demand. | 沿 SRPC 的移动由总需求变化引起。
- A shift of the SRPC is caused by a change in expected inflation or by a supply shock. | SRPC 的移动由预期通胀变化或供给冲击引起。
4. Why the Trade-Off Exists: Demand-Pull Inflation and Labour Markets | 取舍为何存在：需求拉动型通胀与劳动力市场
The trade-off has a clear microeconomic logic. When aggregate demand rises, output expands and firms hire more labour. As unemployment falls, the labour market tightens, so workers and unions gain bargaining power and nominal wages rise. Firms then pass higher wage costs on to consumers through higher prices, producing demand-pull inflation.
这种取舍关系有清晰的微观逻辑。当总需求上升时，产出扩张，企业增雇劳动力。随着失业率下降，劳动力市场趋紧，工人和工会的议价能力增强，名义工资上升。企业随后通过提高价格把更高的工资成本转嫁给消费者，从而产生需求拉动型通胀。
A second channel works through expectations and wage-setting. If workers expect prices to rise, they demand higher nominal wages to protect real wages; firms grant these increases and pass them on, so expectations become self-fulfilling. This is why the same fall in unemployment may generate different inflation outcomes depending on how firmly inflation expectations are anchored.
第二条渠道通过预期与工资设定发挥作用。如果工人预期价格上涨，他们就会要求更高的名义工资以保护实际工资；企业答应这些要求并将其转嫁出去，于是预期具有自我实现的性质。这就是为什么同样的失业率下降，可能因通胀预期锚定的牢固程度不同而产生不同的通胀结果。
The strength of the trade-off depends on several factors:
取舍关系的强度取决于若干因素：
- The slope of the SRPC, which reflects wage and price flexibility | SRPC 的斜率，反映工资与价格的灵活性
- The degree of spare capacity in the labour market | 劳动力市场中闲置产能的程度
- The credibility of the central bank and the anchoring of expectations | 央行的可信度与预期的锚定程度
- The presence of structural bottlenecks in specific sectors | 特定行业是否存在结构性瓶颈
5. The Natural Rate Hypothesis and the Long-Run Phillips Curve | 自然失业率假说与长期菲利普斯曲线
In 1968, Milton Friedman and Edmund Phelps independently challenged the idea of a permanent trade-off. They argued that workers care about real wages, not nominal wages. A sustained attempt to keep unemployment below the natural rate requires ever-higher inflation to keep fooling workers, because once expectations adjust, real wages return to their original level and employment falls back.
1968 年，米尔顿·弗里德曼与埃德蒙·费尔普斯各自独立地对长期取舍关系的观点提出质疑。他们认为，工人关心的是实际工资而非名义工资。若长期试图把失业率压到自然失业率以下，就必须用不断上升的通胀来持续"欺骗"工人，因为一旦预期调整，实际工资就会回到原来的水平，就业也随之回落。
The implication is a vertical long-run Phillips curve (LRPC) at the natural rate of unemployment, also called the NAIRU, the non-accelerating inflation rate of unemployment. In the long run there is no trade-off between unemployment and inflation: the only thing that a sustained demand expansion can achieve is a higher inflation rate.
其含义是：长期菲利普斯曲线（LRPC）在自然失业率处垂直，这一失业率也被称为 NAIRU，即"不加速通胀的失业率"。在长期中，失业与通胀之间不存在取舍关系：持续的扩张性需求政策唯一能带来的结果就是更高的通胀率。
| Feature | 特征 | Short run | 短期 | Long run | 长期 |
|---|---|---|
| Shape of Phillips curve | Downward sloping | Vertical at uₙ |
| Expectations | Given or slow to adjust | Fully adjusted to reality |
| Trade-off? | Yes, temporary | No |
| Effect of demand expansion | Lower unemployment, higher inflation | Higher inflation only |
6. Adaptive Expectations and the Accelerationist View | 适应性预期与加速主义观点
mployment below the natural rate, inflation must rise year after year, because each period's expected inflation is last period' xactly why the natural rate is called the non-accelerating inflation rate of unemployment.
在适应性预期下，人们根据过去经验形成通胀预期，例如 πᵉ = π₋₁。如果政府把失业率维持在自然失业率以下，通胀就必须逐年上升，因为每一期的预期通胀都等于上一期的实际通胀。其结果是加速通胀——这正是自然失业率被称为"不加速通胀的失业率"的原因。
The adjustment process can be traced in stages:
调整过程可以分阶段描述：
- The central bank expands demand; the economy moves up along SRPC₁. | 央行扩张需求，经济沿 SRPC₁ 向上移动。
- Inflation rises above expectations; real wages fall temporarily; employment rises. | 通胀高于预期，实际工资暂时下降，就业上升。
- Workers revise expectations upward; the SRPC shifts up to SRPC₂. | 工人上调预期，SRPC 上移到 SRPC₂。
- Unemployment returns to uₙ, but at a permanently higher inflation rate. | 失业率回到 uₙ，但通胀率永久性更高。
This analysis also explains why central banks regard credibility as a productive asset. If expectations are anchored, a given reduction in unemployment costs less extra inflation; if credibility is lost, the same policy produces a much larger inflation response.
这一分析也解释了为什么央行把可信度视为一种生产性资产。如果预期被锚定，失业率每下降一定幅度所付出的额外通胀代价就更小；而一旦失去可信度，同样的政策会引发大得多的通胀反应。
7. Rational Expectations and Policy Ineffectiveness | 理性预期与政策无效性
Robert Lucas, Thomas Sargent and Neil Wallace extended the argument using rational expectations. If people use all available information, including knowledge of how the government behaves, they will anticipate systematic policy. Announced and credible demand expansion will therefore be built into wages and prices immediately, so output and employment do not respond at all.
罗伯特·卢卡斯、托马斯·萨金特与尼尔·华莱士用理性预期扩展了这一论证。如果人们利用所有可得信息，包括对政府行为方式的了解，他们就会预期到系统性的政策。因此，被宣布且可信的需求扩张会立即反映到工资和价格中，产出与就业完全不会作出反应。
Only unanticipated policy surprises can temporarily lower unemployment, and even then the effect is short-lived. The policy implication is powerful: discretionary demand management is ineffective at raising output systematically, and may simply add inflation volatility. Rules, inflation targets and independent central banks become more attractive than fine-tuning.
只有未被预期到的政策意外才能暂时降低失业率，而且即便在这种情况下，效果也是短暂的。其政策含义非常有力：相机抉择的需求管理无法系统性地提高产出，反而可能只会增加通胀的波动。相较"微调"，规则、通胀目标与独立的央行因此更具吸引力。
Evaluation points that examiners reward here include:
考官在此处看重的评估要点包括：
- Rational expectations are an extreme assumption; information is costly and imperfect. | 理性预期是极端假设，信息是有成本且不完美的。
- Wage contracts and menu costs create inertia, so short-run real effects are likely. | 工资合同与菜单成本造成惯性，因此短期实际效应仍然可能存在。
- Credibility is hard to build and easy to lose, so the model is strongest as a long-run insight. | 可信度的建立很难、失去却很容易，因此该模型作为长期洞见最为有力。
8. Stagflation and Supply Shocks | 滞胀与供给冲击
The stable Phillips curve appeared to break down in the 1970s, when many economies experienced stagflation: rising unemployment alongside rising inflation. The trigger was a series of adverse supply shocks, most famously the oil price shocks of 1973 and 1979, which raised firms' costs of production across the whole economy.
稳定的菲利普斯曲线在 20 世纪 70 年代似乎失效了，当时许多经济体出现了滞胀：失业率与通胀率同时上升。触发因素是一系列不利的供给冲击，其中最著名的是 1973 年和 1979 年的石油价格冲击，它们抬高了整个经济中企业的生产成本。
An adverse supply shock shifts short-run aggregate supply to the left: output falls and the price level rises at the same time. In Phillips curve terms, the SRPC shifts upward, so a higher inflation rate is associated with a higher unemployment rate. This is cost-push inflation, and it is the clearest evidence that the simple inverse relationship is not stable.
不利的供给冲击使短期总供给曲线左移：产出下降的同时价格水平上升。用菲利普斯曲线的语言来说，SRPC 向上移动，于是更高的通胀率伴随着更高的失业率。这就是成本推动型通胀，也是最清楚的证据，说明简单的反向关系并不稳定。
Sources of adverse supply shocks include:
不利供给冲击的来源包括：
- Sharp increases in energy or raw material prices | 能源或原材料价格大幅上涨
- Rises in indirect taxes or the minimum wage | 间接税或最低工资上调
- Exchange rate depreciation raising import prices | 汇率贬值推高进口价格
- Supply chain disruption, strikes or natural disasters | 供应链中断、罢工或自然灾害
9. Money, Inflation and the Quantity Theory | 货币、通胀与货币数量论
The quantity theory of money provides the long-run link between monetary growth and inflation. In its exchange equation form, the identity is:
货币数量论提供了货币增长与通胀之间的长期联系。用交换方程式表示，其恒等式为：
M × V = P × Y
city of circulation, P is the price level and Y is real output. In percentage change form, %ΔM + %ΔV = %ΔP + % ined growth in the money supply in excess of real output growth must show up as inflation.
其中，M 是货币供应量，V 是货币流通速度，P 是价格水平，Y 是实际产出。写成百分比变化形式为：%ΔM + %ΔV = %ΔP + %ΔY。如果流通速度大体稳定，且长期中实际产出按趋势增长率增长，那么货币供应量的持续增长若超过实际产出的增长，就必然表现为通胀。
This is why monetarists argue that inflation is always and everywhere a monetary phenomenon in the long run, and why hyperinflations are consistently associated with rapid money creation to finance government deficits. The relationship is much weaker in the short run, where changes in money supply can affect real output and employment before prices fully adjust.
这就是为什么货币主义者认为，在长期中通胀"永远且处处都是一种货币现象"，也是为什么恶性通胀总是与为政府赤字融资而快速创造货币相联系。这一关系在短期内要弱得多，因为在价格充分调整之前，货币供应量的变化可以影响实际产出与就业。
Two supplementary relationships are useful for evaluation:
有两个补充关系对评估很有用：
- r equation: i ≈ r + πᵉ, linking nominal interest rates, real rates and expected inflation. | 费雪方程：i ≈ r + πᵉ，联系名义利率、实际利率与预期通胀。
- Okun's law: a rise in unemployment of 1 percentage point is associated with roughly 2% lost output relative to trend. | 奥肯定律：失业率上升 1 个百分点，通常伴随产出相对趋势水平损失约 2%。
10. Hysteresis and the Shifting Natural Rate | 滞后效应与移动的自然失业率
A further complication is hysteresis: a prolonged period of high unemployment can raise the natural rate itself. Workers who are out of work for a long time lose skills and become less attractive to employers; insider-outsider effects mean that employed workers protect their own wages rather than helping the unemployed; and discouraged workers withdraw from the labour force altogether.
进一步的复杂因素是滞后效应：长期的高失业本身会抬高自然失业率。长期失业的工人会丧失技能，对雇主而言吸引力下降；内部人—外部人效应意味着在职工人保护自己的工资，而不是帮助失业者；灰心的工人则干脆退出劳动力队伍。
If hysteresis is significant, the long-run Phillips curve is not fixed. A deep recession can shift the LRPC to the right, so that the economy settles at a permanently higher natural rate. Conversely, a sustained period of strong demand and effective active labour market policies can shift the natural rate back down.
如果滞后效应显著，长期菲利普斯曲线就不是固定不变的。一次深度衰退可能使 LRPC 右移，使经济停留在永久性更高的自然失业率上。反之，一段持续强劲的需求期加上有效的积极劳动力市场政策，也可以把自然失业率重新压低。
This is a strong evaluation point: the "no long-run trade-off" conclusion assumes that uₙ is independent of the path the economy takes. If hysteresis is real, the long-run neutrality of demand policy is weakened, and short-run demand management can have lasting supply-side consequences.
这是一个强有力的评估要点："长期不存在取舍关系"的结论假定 uₙ 与经济所走的路径无关。如果滞后效应确实存在，需求政策的长期中性就会被削弱，短期需求管理也可能产生持久的供给侧后果。
11. Policy Implications: Demand-Side versus Supply-Side | 政策含义：需求侧与供给侧
If the LRPC is vertical, demand-side policy cannot permanently reduce unemployment. Expansionary monetary or fiscal policy may give a temporary boost in a deep recession, when there is spare capacity and expectations are not yet anchored upward, but it cannot lower the natural rate. Attempting to do so risks embedding inflation expectations at a higher level.
如果 LRPC 是垂直的，需求侧政策就无法永久性地降低失业。扩张性货币政策或财政政策在深度衰退中或许能带来短暂提振——此时存在闲置产能，且预期尚未向上锚定——但它无法降低自然失业率。强行这样做，反而有使通胀预期固化在更高水平的风险。
The alternative is supply-side policy, which aims to shift the LRPC to the left by reducing the natural rate of unemployment:
替代方案是供给侧政策，通过降低自然失业率使 LRPC 左移：
- Education and training to raise occupational mobility | 教育培训以提高职业流动性
- Reducing benefit traps and improving work incentives | 减少福利陷阱、改善工作激励
- Labour market flexibility and reduced hiring and firing costs | 增强劳动力市场灵活性，降低雇佣与解雇成本
- Infrastructure and competition policy to raise productivity | 基础设施与竞争政策以提高生产率
Supply-side policies have a further advantage: by raising productive capacity, they allow lower unemployment and lower inflation to coexist. Their weaknesses are that they work slowly, may have distributional costs, and do not help in a short-run demand-deficient recession.
供给侧政策还有一个优势：通过提高生产能力，它们使更低的失业与更低的通胀得以并存。其弱点是见效缓慢、可能带来分配成本，而且在短期需求不足型衰退中帮不上忙。
The practical policy framework that emerges is a division of labour:
由此形成的务实政策框架是一种分工：
- Monetary policy targets inflation, supported by an independent central bank. | 货币政策以通胀为目标，并由独立的央行支持。
- Supply-side policy addresses the natural rate of unemployment. | 供给侧政策着力于自然失业率。
- Fiscal policy provides short-run stabilisation when the economy is far from capacity. | 当经济严重偏离产能水平时，财政政策提供短期稳定。
