"Should we enter this category?" usually gets answered with a market size and a gut feeling. Market size is the least useful number in the decision. A large category defended by three entrenched brands is a worse bet than a small one nobody has organised.
Three numbers answer it better, and all three come from a single export.
One: how concentrated is the top
Take the combined share of the top ten brands. Above roughly 60% and you are entering a category with an establishment; below 40% and the category is genuinely open. The number itself matters less than what it implies about how much share you would have to take, and from whom.
A related and more honest measure: how many brands does it take to reach half of category GMV? If the answer is three, you are looking at an oligopoly. If it is forty, you are looking at a fragmented market where distribution and discovery matter more than brand strength.
Two: is the top defended by price or by preference
Compute the realised price index of the top three brands against the category average. This is the number that separates two categories that look identical on a share chart.
Leaders priced well above average hold share through preference. That is expensive to attack — you are fighting brand equity — but it means there is margin in the category and room underneath them.
Leaders priced at or below average hold share by being cheap. That is a category where your cost base decides whether you can compete at all, and where a premium entrant is fighting the whole market's expectations.
Three: which of the three shapes is it
Put the two together and every category falls into one of three shapes:
Concentrated and premium. Few brands, high share, above-average prices. Entry cost is marketing spend, and the opening is usually underneath the leaders rather than against them.
Concentrated and cheap. Few brands, high share, at or below average price. Entry cost is unit economics. If you cannot match their cost base, do not enter.
Fragmented. No brand holds meaningful share. Entry cost is lowest, but so is the ceiling — something about the category resists consolidation, and it is worth understanding what before assuming you will be the one to fix it.
Getting the numbers
One export of the most recent month at "top": 100. That is 100 rows per category, per platform, per month — a few dollars, and the dry-run estimate tells you exactly how many before you spend anything.
Indonesia carries 121 categories back to November 2020, so you can run the same three numbers across several months and see whether the shape is stable or moving. A category that was fragmented two years ago and is consolidating now is a different proposition from one that has been fragmented throughout.
What this does not tell you
It says nothing about margin, logistics, regulatory friction or whether the category is seasonal. It is a shape, not a business case.
What it does do is stop the conversation where most entry decisions go wrong: arguing about whether a category is "big enough" when the real question was always whether the top of it is defended, and how.
Recipe 1.3 in the agent skill is this analysis as a prompt you can paste straight into Claude or ChatGPT.