Inventory Management | 库存管理

📚 Inventory Management | 库存管理

Inventory management is the process of ordering, storing, using and controlling a business’s stock. For Cambridge A-Level Business, it is a core operations management topic because it directly affects costs, cash flow, customer service and profitability.

库存管理是对企业库存进行订购、存储、使用和控制的过程。在剑桥 A-Level 商务课程中，它是一个核心运营管理主题，因为它直接影响成本、现金流、客户服务和盈利能力。

This article explains the main types of inventory, why firms hold stock, how to use inventory control diagrams, and how to evaluate approaches such as just-in-time (JIT) and just-in-case (JIC).

本文将解释库存的主要类型、企业持有库存的原因、如何使用库存控制图，以及如何评价准时制（JIT）和应急库存（JIC）等方法。

1. What Is Inventory? | 什么是库存？

Inventory, also called stock, refers to the goods and materials a business holds for production or sale. In manufacturing, inventory includes raw materials, work-in-progress and finished goods.

库存，也称为存货，指企业为生产或销售而持有的货物和材料。在制造业中，库存包括原材料、半成品和产成品。

For a retailer, inventory is usually finished goods purchased from suppliers and kept ready for customers. For a service business, inventory can be supplies used to deliver the service, such as cleaning materials in a hotel.

对于零售商而言，库存通常是从供应商购入并准备销售给顾客的产成品。对于服务企业，库存可以是用于提供服务的耗材，例如酒店的清洁用品。

In accounting, inventory is a current asset, but holding too much inventory ties up cash and increases storage risk. Effective inventory management therefore balances availability with cost control.

在会计中，库存是一项流动资产，但持有过多库存会占用现金并增加存储风险。因此，有效的库存管理需要在可用性和成本控制之间取得平衡。

2. Types of Inventory | 库存类型

Businesses classify inventory according to its stage in the production process. The three main types are raw materials, work-in-progress and finished goods.

企业根据生产过程中的阶段对库存进行分类。三种主要类型是原材料、半成品和产成品。

Raw materials are purchased inputs waiting to be used in production.

原材料是等待用于生产的采购投入品。
Work-in-progress (WIP) consists of partly finished goods that are still on the production line.

半成品（WIP）指仍在生产线上的部分完成产品。
Finished goods are completed products ready for sale to customers.

产成品是已完工、可供销售给顾客的产品。

Some firms also hold maintenance, repair and operating (MRO) supplies, such as spare parts, lubricants and safety equipment. These items do not become part of the final product but are necessary for operations.

一些企业还持有维护、修理和运营（MRO）物料，如备件、润滑油和安全设备。这些物品不构成最终产品的一部分，但却是运营所必需的。

In a Cambridge exam, you may be asked to identify which type of inventory is being described. Always link the type to the production stage and the business context.

在剑桥考试中，你可能需要判断所描述的是哪类库存。始终将库存类型与生产阶段和企业背景联系起来。

3. Why Businesses Hold Inventory | 企业持有库存的原因

Businesses hold inventory for several operational and commercial reasons. The most common reason is to meet customer demand without delay.

企业持有库存有几个运营和商业原因。最常见的原因是为了能够立即满足客户需求。

Inventory acts as a buffer against uncertainty in demand and supply. If a supplier delivers late or demand suddenly rises, buffer stock prevents stock-outs and lost sales.

库存可以作为应对需求和供应不确定性的缓冲。如果供应商延迟交货或需求突然上升，缓冲库存可以防止缺货和销售损失。

Firms may also hold inventory to gain economies of scale through bulk buying. Large orders can secure volume discounts and lower unit purchase costs.

企业也可能通过批量采购持有库存以获得规模经济。大额订单可以获得数量折扣并降低单位采购成本。

For seasonal businesses, inventory is built up before peak periods. For example, a toy retailer holds extra stock before the Christmas season to satisfy a sharp increase in demand.

对于季节性企业，库存会在旺季之前积累。例如，玩具零售商在圣诞节前持有额外库存，以满足需求的急剧增长。

Finally, holding work-in-progress allows continuous production. Without WIP, machines may stand idle between production stages, reducing efficiency.

最后，持有半成品可以保证生产连续进行。如果没有半成品，机器可能在生产阶段之间闲置，降低效率。

4. Costs of Holding Inventory | 库存持有成本

Holding inventory is not free. Businesses face several categories of inventory-related costs, and managers must balance them against the benefits of holding stock.

持有库存并非没有成本。企业面临几类与库存相关的成本，管理者必须将这些成本与持有库存的收益进行权衡。

Ordering costs are the costs of placing and receiving an order, such as administration, transport and inspection. Each new order increases ordering costs.

订购成本是下达和接收订单的成本，例如行政管理、运输和检验费用。每下一笔新订单都会增加订购成本。

Holding costs, also called carrying costs, include storage rent, insurance, security, handling, electricity for cold storage, and the opportunity cost of capital tied up in stock.

持有成本，也称为储存成本，包括仓储租金、保险、安保、搬运、冷藏电费以及占用在库存中的资本机会成本。

Stock-out costs occur when a business runs out of stock. These include lost sales, lost customer goodwill, emergency ordering costs and possible production stoppages.

缺货成本发生在企业库存耗尽时。这些成本包括销售损失、客户商誉损失、紧急订购成本以及可能的生产中断。

There is also the risk of obsolescence and spoilage. Products such as fashion clothing, electronics or fresh food lose value if they are stored too long.

还存在过时和变质的风险。服装、电子产品或新鲜食品等产品如果存放过久就会贬值。

5. Inventory Control Diagrams | 库存控制图

An inventory control diagram is a visual tool that shows how stock levels change over time. It helps managers plan ordering and avoid stock-outs.

库存控制图是一种可视化工具，显示库存水平随时间的变化。它帮助管理者规划订购并避免缺货。

In a typical diagram, the horizontal axis shows time and the vertical axis shows stock level. Stock falls at a steady rate as items are used or sold, then rises when a new order arrives.

在典型图表中，横轴表示时间，纵轴表示库存水平。随着物品被使用或销售，库存以稳定的速度下降，然后在收到新订单时上升。

Key points on the diagram include maximum stock level, reorder level, lead time and buffer stock. The reorder level is the stock level at which a new order must be placed.

图表上的关键点包括最高库存水平、再订货水平、交货时间和缓冲库存。再订货水平是必须下新订单时的库存水平。

Lead time is the time between placing an order and receiving it. During lead time, stock continues to fall, so the reorder level must be high enough to cover expected usage.

交货时间是下订单到收到货物之间的时间。在交货时间内，库存继续下降，因此再订货水平必须足够高以覆盖预期用量。

Buffer stock is the minimum stock held as a safety margin. If demand is higher than expected or delivery is late, buffer stock is used before the business runs out.

缓冲库存是为安全边际而持有的最低库存。如果需求高于预期或交货延迟，缓冲库存在企业缺货之前会被使用。

6. Buffer Stock and Reorder Level | 缓冲库存与再订货水平

Buffer stock is the emergency stock held to protect against uncertainty. It is not intended for normal use; it exists to prevent stock-outs when conditions are worse than expected.

缓冲库存是为防范不确定性而持有的应急库存。它不是用于正常使用，而是为了在情况比预期更糟时防止缺货。

The reorder level can be calculated using the following relationship:

再订货水平可以使用以下关系式计算：

Reorder level = (Average usage per period × Average lead time) + Buffer stock

再订货水平 =（每期平均用量 × 平均交货时间）+ 缓冲库存

For example, if a firm uses 200 units per day, the lead time is 5 days, and buffer stock is 300 units, then the reorder level is (200 × 5) + 300 = 1,300 units.

例如，如果一家企业每天使用 200 单位，交货时间为 5 天，缓冲库存为 300 单位，那么再订货水平为（200 × 5）+ 300 = 1,300 单位。

Businesses must decide how much buffer stock to hold. Too little increases stock-out risk; too much raises holding costs. The optimal buffer depends on how predictable demand and lead time are.

企业必须决定持有多少缓冲库存。过少会增加缺货风险；过多会提高持有成本。最佳缓冲量取决于需求和交货时间的可预测性。

7. Economic Order Quantity (EOQ) | 经济订货批量（EOQ）

The economic order quantity (EOQ) is the order size that minimises the total cost of ordering and holding inventory. It is a quantitative tool used when demand is stable and known.

经济订货批量（EOQ）是使订购成本和库存持有成本总和最小的订货数量。它是一种在需求稳定且已知时使用的定量工具。

The EOQ formula is:

EOQ 公式为：

EOQ = √(2 × D × O ÷ C)

Where D is annual demand in units, O is the ordering cost per order, and C is the annual holding cost per unit.

其中 D 是年需求量（单位），O 是每笔订单的订购成本，C 是每单位的年持有成本。

The logic of EOQ is that ordering costs fall when larger orders are placed less frequently, but holding costs rise because average stock is higher. EOQ finds the balance point between these two costs.

EOQ 的逻辑是：下大订单并减少订货次数可以降低订购成本，但由于平均库存升高，持有成本会上升。EOQ 找到了这两种成本之间的平衡点。

However, EOQ has limitations. It assumes constant demand, constant ordering costs and no quantity discounts. In practice, demand fluctuates and suppliers may offer discounts for larger orders, so firms may not follow EOQ exactly.

然而，EOQ 也有局限性。它假设需求恒定、订购成本恒定且没有数量折扣。实际上，需求会波动，供应商可能对大订单提供折扣，因此企业可能不完全按照 EOQ 执行。

8. Just-in-Time (JIT) Inventory Management | 准时制（JIT）库存管理

Just-in-time (JIT) is a lean production method where inventory is delivered exactly when it is needed in the production process. The aim is to hold little or no buffer stock.

准时制（JIT）是一种精益生产方法，即库存恰好在生产过程需要时送达。其目标是持有很少或不持有缓冲库存。

JIT reduces holding costs and releases cash tied up in stock. It also reduces waste, storage space and the risk of obsolescence or spoilage.

JIT 可以降低持有成本并释放占用在库存中的现金。它还能减少浪费、仓储空间以及过时或变质风险。

For JIT to work, a business needs highly reliable suppliers, frequent deliveries, flexible employees and excellent quality control. A late delivery can stop the entire production line.

要使 JIT 有效运行，企业需要高度可靠的供应商、频繁的配送、灵活的员工和出色的质量控制。一次延迟交货可能导致整条生产线停工。

JIT also requires strong relationships with suppliers. Many firms using JIT work with a small number of trusted suppliers located close to their factories.

JIT 还要求与供应商建立牢固的关系。许多采用 JIT 的企业会与少数位于工厂附近的可靠供应商合作。

In a Cambridge essay, evaluate JIT by comparing its cost savings against its vulnerability to supply chain disruption.

在剑桥考试的文章题中，评价 JIT 时应将其成本节约与供应链中断的脆弱性进行对比。

9. Just-in-Case (JIC) vs Just-in-Time | 应急库存（JIC）与准时制（JIT）对比

Just-in-case (JIC) is the opposite approach to JIT. A business holds large buffer stocks so it can continue operating even if demand rises sharply or suppliers fail.

应急库存（JIC）是与 JIT 相反的方法。企业持有大量缓冲库存，以便即使需求急剧上升或供应商出现问题，也能继续运营。

The table below summarises the main differences between JIT and JIC:

下表总结了 JIT 与 JIC 之间的主要区别：

Feature	JIT	JIC
Buffer stock	Minimal or zero	Large safety stock
Holding costs	Low	High
Flexibility	Less able to cope with sudden demand	Better able to meet unexpected demand
Supplier dependence	Very high	Lower
Risk	Supply chain disruption can stop production	Stock may become obsolete or spoiled

The choice between JIT and JIC depends on the business context. A car manufacturer with reliable suppliers may prefer JIT, while a hospital storing critical medicines may prefer JIC because stock-outs could be life-threatening.

选择 JIT 还是 JIC 取决于企业背景。拥有可靠供应商的汽车制造商可能更倾向于 JIT，而储备关键药品的医院可能更倾向于 JIC，因为缺货可能危及生命。

10. Factors Affecting Inventory Management Decisions | 影响库存管理决策的因素

There is no single best inventory system for all businesses. Managers must consider several internal and external factors.

对所有企业而言，并不存在唯一最佳的库存系统。管理者必须考虑多个内部和外部因素。

Product type is important. Perishable goods such as fresh food and newspapers require fast turnover and small buffer stocks. Durable goods such as machinery parts can be stored longer.

产品类型很重要。新鲜食品和报纸等易腐商品需要快速周转和较少的缓冲库存。机械零件等耐用品可以存放更久。

Demand predictability matters. If demand is stable, a firm can use smaller buffer stocks. If demand is highly volatile, a firm may need more safety stock or a more responsive ordering system.

需求的可预测性也很重要。如果需求稳定，企业可以使用较少的缓冲库存。如果需求波动很大，企业可能需要更多安全库存或反应更快的订购系统。

Supplier reliability affects reorder levels. Unreliable suppliers force businesses to hold more buffer stock or use JIC. Reliable suppliers make JIT possible.

供应商可靠性会影响再订货水平。不可靠的供应商迫使企业持有更多缓冲库存或使用 JIC。可靠的供应商使 JIT 成为可能。

Technology also shapes inventory management. Barcode scanners, RFID tags and real-time inventory software help firms track stock accurately and reorder automatically.

技术也会影响库存管理。条形码扫描器、RFID 标签和实时库存软件帮助企业准确追踪库存并自动再订货。

Finally, the cost of storage and the firm’s financial position matter. A business with weak cash flow cannot afford to tie up large amounts of money in inventory.

最后，存储成本和企业财务状况也很重要。现金流紧张的企业无法承受将大量资金占用在库存上。

11. Inventory Management and Business Performance | 库存管理与企业绩效

Effective inventory management improves business performance by reducing costs, freeing cash and increasing customer satisfaction.

有效的库存管理通过降低成本、释放现金和提高客户满意度来改善企业绩效。

One key measure is inventory turnover, calculated as:

一个关键指标是库存周转率，计算公式为：

Inventory turnover = Cost of sales ÷ Average inventory

库存周转率 = 销售成本 ÷ 平均库存

A higher inventory turnover generally means stock is sold quickly, reducing holding costs and the risk of obsolescence. However, if turnover is too high, the business may be understocking and losing sales.

较高的库存周转率通常意味着库存销售迅速，降低了持有成本和过时风险。然而，如果周转率过高，企业可能库存不足并失去销售机会。

Good inventory management also improves cash flow. Money spent on excess stock is cash that cannot be used for wages, marketing or new equipment.

良好的库存管理还能改善现金流。花在多余库存上的资金无法用于工资、营销或新设备。

From a customer perspective, having the right product at the right time increases loyalty. Stock-outs frustrate customers and may send them to competitors.

从客户角度看，在正确的时间提供正确的产品可以提高忠诚度。缺货会让顾客失望，并可能将他们推向竞争对手。

Therefore, inventory decisions are not just about cost. They affect operational efficiency, customer service and the overall competitiveness of the business.

因此，库存决策不仅仅是成本问题。它们会影响运营效率、客户服务和企业整体竞争力。

12. Evaluation and Exam Tips | 评价与备考建议

In Cambridge A-Level Business, exam questions often ask you to evaluate the benefits and drawbacks of holding inventory or to assess the suitability of JIT for a given business.

在剑桥 A-Level 商务考试中，题目经常要求你评价持有库存的好处和弊端，或评估 JIT 对某家企业的适用性。

Use the following evaluation framework: always link the inventory method to the business context, such as industry, product type, demand pattern, supplier reliability and financial capacity.

使用以下评价框架：始终将库存方法与商业背景联系起来，例如行业、产品类型、需求模式、供应商可靠性和财务能力。

When writing an essay, build a balanced argument. For example, JIT reduces costs but increases supply risk; JIC increases security but raises holding costs and waste.

写文章时要构建平衡的论证。例如，JIT 降低了成本但增加了供应风险；JIC 提高了安全性但增加了持有成本和浪费。

Use quantitative methods such as reorder level and EOQ to support your analysis. Show the formula and interpret the result in the business context.

使用再订货水平和 EOQ 等定量方法来支持你的分析。展示公式并在商业背景下解释结果。

Finally, include a reasoned conclusion. The best inventory strategy is contingent on circumstances, not universal. A strong answer recognises trade-offs and makes a justified recommendation.

最后，给出有理有据的结论。最佳库存策略取决于具体情况，并非普遍适用。优秀的答案应认识到权衡取舍并作出有理有据的建议。

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Inventory Management | 库存管理