ABC Analysis: Which Stock Deserves Your Attention

Attention is the scarce resource

You cannot manage two thousand products carefully. Nobody can. What actually happens in a shop with a large catalogue is that attention gets spread thinly and arbitrarily — you think hard about whatever caused a problem last week, and give equal consideration to a line generating a large share of your profit and one that sells twice a year.

Meanwhile a small minority of your products carries nearly all of your gross profit. Those are the lines where a stockout is genuinely expensive, where a small pricing change moves real money, and where an inventory error costs the most.

ABC analysis is the method for finding out which ones they are, and it takes an afternoon.

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The technique

Rank every product by its annual contribution, run a cumulative total down the list, and cut it into three classes:

• A — the lines making up roughly the first 80% of total contribution
• B — the next 15%
• C — the remaining 5%

The proportions of products in each class are what surprise people. In most retail catalogues, the A class is a small fraction of the lines. Everything else is B and C.

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Rank by margin, not revenue

This is the step that decides whether the analysis helps or misleads, and it is where most attempts go wrong.

Rank by gross profit contribution: units sold × margin per unit.

Ranking by revenue rewards volume regardless of what you keep. Consider two lines:

	Line X	Line Y
Units sold in a year	4,000	400
Margin per unit	2	30
Revenue	High	Modest
Gross profit contribution	8,000	12,000

By revenue, Line X looks like the more important product by a wide margin. By profit contribution, Line Y earns you half again as much. Rank by revenue and your analysis instructs you to protect availability, negotiate hard, and count weekly on your thinnest-margin products — the ones where a stockout costs you least per unit.

This matters most in exactly the businesses that have the most products: supermarkets and general stores, where price-transparent staples dominate revenue while the profit sits somewhere less obvious. If your catalogue includes airtime, staple grains, or anything else customers price-check, the two rankings will look very different.

Cost price on every product is therefore a precondition, not an optional refinement. Without it you can rank by revenue and not by profit, which is the wrong ranking.

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A worked example

Ten products, ranked by annual gross profit contribution, total 4,000.

Rank	Contribution	Cumulative	Cumulative %	Class
1	1,400	1,400	35%	A
2	1,000	2,400	60%	A
3	800	3,200	80%	A
4	350	3,550	89%	B
5	250	3,800	95%	B
6	120	3,920	98%	C
7	40	3,960	99%	C
8	25	3,985	99.6%	C
9	10	3,995	99.9%	C
10	5	4,000	100%	C

Three products — 30% of the range — carry 80% of the gross profit. Five products, half the catalogue, contribute 5% between them.

Read the bottom of that table carefully, because it contains the counterintuitive point. Product 10 contributes almost nothing measurable. It still probably belongs in your range. More on that below.

With a real catalogue of hundreds or thousands of lines the concentration is usually sharper than this, and the exercise of seeing your own numbers laid out this way tends to be genuinely surprising — including which lines you assumed were central and are not.

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What you actually change

An analysis that does not change behaviour is a spreadsheet. Four things change, per class.

Counting frequency

A lines monthly, B quarterly, C twice a year. Errors on A lines are expensive and worth finding quickly; errors on C lines cost less than the labour of counting them often. This is also the natural way to build a cycle-count rotation, which our stocktake checklist covers as a method.

Reorder discipline

A lines get a per-product reorder point, calculated from sales rate and supplier lead time, reviewed quarterly. C lines can inherit a rough default or be ordered on demand. Doing this properly for A lines only is the highest-return action available from an ABC analysis, and it is finishable in an afternoon — the arithmetic is in our reorder points guide.

Buying approval

A large order on an A line deserves the owner's or a manager's attention. A large order on a C line is where dead stock comes from, and it usually happens because a supplier offered a discount and nobody senior looked at it. Requiring a second pair of eyes above a value threshold on non-A lines prevents most of it. Our post on dead stock covers what that accumulation costs.

Stockout tolerance

Protect A-line availability nearly absolutely. Accept that C lines will occasionally be unavailable and tell staff what to say. Trying to guarantee availability across an entire catalogue is how businesses end up with cash tied up everywhere and still out of stock on the things that matter.

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The C-class trap

The most common mistake after a first ABC analysis is deciding to cut the C lines. It looks obviously correct — half the catalogue producing five percent of the profit, why hold it?

Because contribution is measured per line, and some C lines are not there to contribute on their own. They are:

• Assortment. The reason a customer chooses your shop over the one down the road is often that you have the odd thing they occasionally need. Remove enough of those and you lose the visit, not just the item.
• Attachments. The small accessory bought alongside a large purchase. Its own margin is trivial; its absence can cost you the sale it was attached to.
• Range credibility. A shop visibly missing obvious items reads as failing, and customers reduce their expectations accordingly.

None of that shows up in a per-line contribution figure, and the analysis cannot warn you about it.

So cut depth, not breadth. Stop holding three months of C-class stock. Order in small quantities, accept occasional gaps, stop spending management attention on it. Keep the range and stop funding it.

The C lines genuinely worth removing are the ones failing on their own terms: no sales at all over a meaningful window, no assortment logic, no attachment role. That is a dead stock question rather than an ABC question.

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Running it

The quick version, worth doing first: run it on categories rather than products. Fewer rows, quicker to interpret, and often the more revealing result — that a category everyone treats as central contributes little, or that an unglamorous one is carrying the business. Then go product-level inside the two or three categories that turn out to matter.

The inputs: units sold over the last twelve months (or your best clean period), selling price, and cost price. Margin per unit is selling price minus cost price. Contribution is units sold times margin per unit.

In Zeneva: margin analysis and inventory valuation both read from the cost price recorded on each product, so the ranking is available once that field is populated. Category breakdown gives you the quick version above. If you use Zen AI, asking which products contribute most to profit over the last year returns the ranking directly — but the answer is only as good as your cost prices, which is worth remembering before acting on it.

Cadence: quarterly. Between runs, watch the boundaries — a line moving from B into A deserves a proper reorder point, and an A line slipping is an early warning worth investigating while it still has value.

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What a first pass should produce

Not a filing document. Three concrete outputs:

1. A written list of your A lines. Put it somewhere staff can see. A surprising amount of value comes simply from everyone knowing which products must never be out of stock.
2. Calculated reorder points on those lines. One afternoon. This is where the return is.
3. One rule about buying non-A lines. A value threshold above which someone else looks at the order.

That is a realistic afternoon's work with effects that persist. The failure mode is producing a beautiful classification and changing nothing about how the shop is run — in which case the honest verdict is that you spent an afternoon confirming which products sell well.

For the forecasting layer that sits on top of this, our guide to predicting demand covers reading the direction of travel rather than the current ranking.

Margin analysis and category breakdown read straight from the cost prices you record, so the ranking above becomes a report you open rather than a spreadsheet you build — see what each plan includes.