What you'll learn
Inventory is money sitting still. Every unit held has been paid for and has not yet been sold, so stock ties up working capital, occupies space, and risks deterioration or obsolescence — and yet holding too little stops production and loses sales. The whole topic is the management of that tension, and for a Caribbean business it is sharpened by import lead times that firms in larger economies never face. This guide covers the reasons for holding stock and the costs of doing so, stock control levels and the calculations behind them, just-in-time and its trade-offs, the supply chain and supplier relationships, logistics, and the specific position of import-dependent island businesses. It sits in Unit 2.
Key terms and definitions
Inventory (stock) — goods held as raw materials, work in progress or finished goods.
Raw materials — inputs bought but not yet used in production.
Work in progress — partly finished goods within the production process.
Finished goods — completed output not yet sold.
Buffer stock — a minimum level held to absorb unexpected demand or delivery delay.
Reorder level — the stock level at which a new order is placed.
Lead time — the period between placing an order and receiving it.
Reorder quantity — the amount ordered each time.
Maximum stock level — the largest quantity the business will hold.
Stockout — running out of an item that is needed.
Just-in-time (JIT) — receiving inputs only as they are required, holding minimal stock.
Stock turnover — the number of times inventory is sold and replaced in a period.
Supply chain — the sequence of organisations and activities moving a product from raw material to final customer.
Logistics — the movement and storage of goods through the supply chain.
Procurement — the process of sourcing and purchasing inputs.
Core concepts
Why hold stock, and what it costs
Reasons to hold. To meet demand without delay. To allow production to continue while awaiting delivery. To absorb fluctuation in demand or in supply. To obtain bulk purchase discounts. To guard against price rises. And to cover seasonal peaks.
The costs of holding. Capital tied up in goods that have been paid for and not yet sold, which is the largest cost and the least visible. Storage — space, handling, refrigeration, security. Insurance. Deterioration for perishables. Obsolescence, where stock loses value because tastes or technology move on. And theft or damage.
The costs of not holding enough. A stockout halts production, loses the immediate sale, and may lose the customer permanently. Emergency replenishment is bought at a premium and shipped at a premium. And reputation suffers where a business becomes known for being out of stock.
The management task is to hold the least stock consistent with not running out — and the right level depends on lead time, on how predictable demand is, and on what a stockout would cost.
Stock control levels
Reorder level is the point at which a new order is placed, and it must cover usage during the lead time plus the buffer:
Reorder level = (Average daily usage × Lead time in days) + Buffer stock
Worked example. A business uses 50 units a day, lead time is 12 days, and it holds a buffer of 200 units.
Reorder level = (50 × 12) + 200 = 600 + 200 = 800 units
When stock falls to 800, the order is placed. During the 12 days that follow, 600 units are used, leaving the 200-unit buffer as the delivery arrives.
Buffer stock is the insurance. It should be larger where lead times are long or unreliable, where demand fluctuates, and where a stockout would be costly — which is precisely why import-dependent businesses hold more than textbook models suggest.
Stock turnover measures how hard inventory is working:
Stock turnover = Cost of sales ÷ Average inventory
Worked example. Cost of sales $600,000, average inventory $75,000:
Stock turnover = $600,000 ÷ $75,000 = 8 times a year
Stock is therefore sold and replaced roughly every six or seven weeks. Higher turnover generally means capital is working harder, but pushed too far it raises stockout risk. Appropriate levels differ sharply by trade: a fresh produce retailer must turn stock many times faster than a furniture dealer.
Just-in-time
JIT receives inputs only as production requires them, holding minimal stock.
Benefits. Working capital released. Storage space and cost reduced. Less waste from deterioration and obsolescence. And quality problems surface immediately rather than being buried in a large stock of already-made components.
Requirements, which is where most answers stop too early. JIT needs reliable suppliers, short and predictable lead times, dependable transport, accurate demand forecasting, good information systems, and close supplier relationships — frequently with suppliers located nearby.
Risks. A single delivery failure halts production, because there is no buffer. The system is vulnerable to transport disruption, industrial action, weather and supplier failure. Small, frequent deliveries can cost more in transport than bulk ones. And bulk discounts are forfeited.
The regional judgement matters. Full JIT is difficult for a business importing inputs across water, where lead times are long and shipping is subject to weather and port congestion. A modified approach — JIT principles applied to locally sourced inputs, with substantial buffers held on imported ones — is usually the defensible recommendation, and saying so demonstrates judgement rather than recited theory.
The supply chain
The supply chain is the whole sequence from raw material to final customer: suppliers, manufacturer, distributors, retailers, customer. Supply chain management coordinates it so that goods flow efficiently and information flows back the other way.
Upstream concerns suppliers and inputs; downstream concerns distribution and customers.
Effective supply chain management reduces total cost rather than cost at one point — squeezing a supplier's price while forcing them to hold the stock simply moves cost rather than removing it, and a supplier operating on impossible margins eventually fails or cuts quality.
Supplier relationships
Two approaches, and the choice has consequences.
Adversarial purchasing treats each order as a separate negotiation, uses multiple suppliers, and drives price down. It keeps pressure on price and avoids dependence, but it forfeits cooperation, information sharing and priority when supply is tight.
Partnership purchasing builds long-term relationships with fewer suppliers, sharing forecasts and working jointly on quality and cost. It supports JIT, improves reliability and quality, and earns priority in a shortage — at the cost of dependence on fewer sources and less price pressure.
Supplier selection should weigh price, quality, reliability, lead time, capacity, financial stability and location together. Choosing on price alone is the commonest and most expensive purchasing error, because an unreliable cheap supplier costs more through stockouts and quality failures than it saves per unit.
Single sourcing simplifies the relationship and deepens cooperation but concentrates risk. Multiple sourcing spreads risk and preserves price pressure at the cost of divided volume and weaker relationships.
Logistics
Logistics moves and stores goods through the chain, covering transport mode, warehousing, handling and delivery.
For regional businesses the decisive features are that sea freight is cheaper and slower and air freight dearer and faster, so the choice depends on value density and urgency; that customs procedures add time that must be built into lead time rather than discovered; that port congestion and weather make lead times variable as well as long; and that cold chain requirements for perishables add cost and risk at every transfer.
The Caribbean position
Several factors recur and should be named as evidence rather than asserted.
Import dependence means many inputs arrive by sea with lead times measured in weeks rather than days. Lead time variability matters more than its length, because an unpredictable six weeks requires a larger buffer than a reliable eight. Small order volumes give limited bargaining power with distant suppliers and may not meet minimum order quantities. Hurricane season interrupts shipping and justifies pre-season stock building. Limited local supplier bases restrict substitution when a supplier fails. Warehousing cost and humidity affect what can be stored and for how long. And the CSME makes regional sourcing easier in principle, though shipping between islands remains slow and costly.
The overall consequence is that regional businesses rationally hold more inventory than a textbook model prescribes, and an answer that recommends aggressive stock reduction without acknowledging this has misread the situation.
Worked examples
Example 1: Reorder level (calculation)
Question: "A business uses 50 units a day, lead time is 12 days and buffer stock is 200 units. Calculate the reorder level and explain it." (8 marks)
Working.
Reorder level = (Average daily usage × Lead time) + Buffer stock = (50 × 12) + 200 = 600 + 200 = 800 units
Explanation. When stock falls to 800 units the order is placed. Over the following 12 days the business uses 600 units, arriving at the 200-unit buffer just as the delivery lands. The buffer exists so that a delivery arriving late, or demand running above 50 a day, does not cause a stockout. Add the judgement: if the supplier is overseas and lead time varies between 12 and 20 days, a 200-unit buffer is inadequate — variability matters more than average length, and the buffer should cover the worst plausible delay rather than the typical one.
Example 2: Stock turnover (calculation)
Question: "Cost of sales is $600,000 and average inventory is $75,000. Calculate stock turnover and comment." (8 marks)
Working.
Stock turnover = Cost of sales ÷ Average inventory = $600,000 ÷ $75,000 = 8 times a year
Comment. Stock is sold and replaced roughly every six or seven weeks, so capital is not sitting idle for long. Whether 8 is good depends entirely on the trade: a supermarket would regard it as very slow, a furniture retailer as reasonable. Compare against the previous year and against competitors rather than judging the figure alone. Note the tension — raising turnover releases working capital but increases stockout risk, and for an import-dependent business the safe level is lower than for one buying locally.
Example 3: JIT evaluation
Question: "Evaluate the adoption of just-in-time by a Caribbean manufacturer importing most of its raw materials." (20 marks)
Outline. Set out the benefits: working capital released, storage cost and space reduced, less deterioration and obsolescence, and quality problems surfacing immediately. Then the requirements, and this is where the answer turns: JIT needs reliable suppliers, short predictable lead times and dependable transport. For a manufacturer importing by sea, lead times are long and variable, shipping is subject to weather and port congestion, and there is no local alternative supply to fall back on. A single delayed vessel halts production entirely. Add that small, frequent deliveries cost more in freight than consolidated ones, which reverses one of JIT's usual savings. Conclude with the modified recommendation — JIT principles applied to locally sourced inputs and to internal work-in-progress, with substantial buffers retained on imported materials — and state explicitly that full JIT transplanted from a large land-based economy would be a misapplication here.
Common mistakes and how to avoid them
Treating stock as an asset with no cost. It ties up capital, occupies space and can deteriorate.
Forgetting buffer stock in the reorder calculation. Reorder level covers lead-time usage plus the buffer.
Recommending JIT without stating its requirements. Reliable suppliers, short lead times and dependable transport are preconditions.
Assuming higher stock turnover is always better. It raises stockout risk, and appropriate levels differ by trade.
Judging a turnover figure without comparison. Compare across years and against the trade.
Choosing suppliers on price alone. Unreliability costs more through stockouts than it saves per unit.
Confusing lead time length with lead time variability. Variability is what determines buffer size.
Ignoring import lead times in regional recommendations. Aggressive stock reduction may be the wrong advice entirely.
How this links to your Internal Assessment
Inventory is one of the more measurable project themes, because even businesses keeping few records know what they hold and how often they run out.
Ask what the business actually does: how it decides when to reorder, whether a reorder level exists formally or by judgement, what lead times are, how often it runs out, and what a stockout costs. Owners answer these concretely because the problems are immediate.
If you can obtain figures, calculate stock turnover across two or three years and reorder levels from usage and lead time, then compare the calculated level with what the business actually does. The gap is frequently the finding — many small businesses reorder by eye and hold either far too much capital in stock or too little buffer against a shipping delay. Explaining that gap using lead-time variability is exactly the analysis the assessment rewards.
Exam technique for inventory and supply chain management
State the formula before substituting, and label answers with units.
Include buffer stock in every reorder-level calculation.
Give JIT's requirements and risks alongside its benefits.
Judge turnover by comparison, not in isolation.
Weigh supplier selection on reliability and lead time as well as price.
Use import lead times and their variability as concrete regional evidence.
Distinguish reducing total supply chain cost from shifting cost onto a supplier.
Watch the command word: calculate wants the working, explain wants the mechanism, evaluate wants a judgement acknowledging regional conditions.
Quick revision summary
Stock is held to meet demand, sustain production, absorb fluctuation, capture bulk discounts and cover seasonal peaks, at the cost of tied-up capital, storage, insurance, deterioration, obsolescence and theft — while holding too little risks a stockout that halts production and may lose the customer permanently. Reorder level equals average daily usage multiplied by lead time plus buffer stock, and buffer size should reflect lead-time variability rather than its average length. Stock turnover is cost of sales divided by average inventory, and is judged by comparison across years and against the trade rather than in isolation. Just-in-time releases working capital, cuts storage and surfaces quality problems immediately, but requires reliable suppliers, short predictable lead times, dependable transport and accurate forecasting, and a single delivery failure halts production — which makes a modified approach, applying JIT to local inputs while holding buffers on imported ones, the defensible recommendation regionally. Supply chain management reduces total cost rather than shifting it onto suppliers, and supplier relationships may be adversarial, keeping price pressure, or partnership-based, supporting reliability, quality and JIT at the cost of dependence. Logistics choices weigh sea against air freight by value density and urgency, and must build customs, port congestion and weather into lead time. Import dependence, lead-time variability, small order volumes, hurricane season, limited local supplier bases and humidity all mean regional businesses rationally hold more inventory than textbook models prescribe.