Customer Concentration Risk

Six clients, one of them 48% of the year. On the arithmetic that measures this properly, that is not six clients. It is 3.23.

The figure is the standard measure of concentration and it answers the question a client count cannot: how many independent sources of income you actually have. A list of six names feels like six. It behaves like three, and the difference is invisible from the list, which is exactly why almost nobody in this position has ever worked it out.

Beside it the page answers the practical version: if the biggest client goes, what is left, and does it still cover what you have to pay anyway. Rent, salaries, software, insurance — the costs that do not care how many clients you have.

It says nothing about whether the concentration is a fault, because it is not automatically one. One long, good, well-paying client is a fact to know rather than a problem to solve, and plenty of excellent businesses run on two or three. What is dangerous is not knowing the size of the gap between having them and not.

So it does not tell you to drop anybody, chase anybody, or diversify. It does not know which of your clients is about to leave, which relationship is ten years old and which is ten weeks, or which of them is a pleasure to work for. It measures the shape of one year, and the shape is one input among several.

Every client is listed largest first with a share and a running total, which is usually where it becomes obvious: on the figures it ships with, three names out of six are 84% of the money.

Save as many versions as you like and put any two side by side, figure against figure, with the better one on each line marked and the difference in its own column. That screen is the one that decides things, and it is the part a free calculator cannot do at all. Concentration moves slowly and then all at once, so two years side by side is the comparison worth having.

One HTML file. No account, no subscription, no internet needed. Opens on Windows, Mac and Android; the readme explains the extra step on iPhone and iPad, where Apple blocks JavaScript in downloaded files and every tool of this kind is affected.

Everything lives in your browser on your device. Nothing is uploaded, which is why it works offline and why nobody else can see your figures — and it also means clearing your browsing data deletes it. The tool does not pretend otherwise: the header shows how long since your last export at all times, turns amber after three days and red after seven, and export is one click that produces a plain file you keep.