Sizing the Small-Business Advertiser Base on Facebook

In a product manager interview at Meta, you are asked how many small businesses advertise on Facebook. You have no data to look up. Lay out a structure, state every assumption, do the arithmetic out loud, and check whether your final number is believable. ```hint Choose a funnel you can defend Decide whether to work down from the businesses that exist to the ones that pay, or up from the ad side, based on which inputs you can justify out loud. Before using one average for the whole world, ask whether business density and ad adoption are similar everywhere. ``` ### Clarifying Questions - Should the estimate cover every country where Facebook is available, or one market such as the US? - What counts as a small business: is there an employee limit, and do sole proprietors and side businesses count? - What counts as using ads: buying any ad or boosted post in the past year, or spending in a given month? And does an ad bought through Meta's tools that runs only on Instagram count? - Are we counting distinct businesses, or ad accounts, of which one business or agency can hold several? ### What a Strong Answer Covers - Definitions of "small business", "using ads" and the time window, agreed before any numbers - A clear equation with segmentation that changes the answer, such as market type or business size - Every input labeled as an assumption with round numbers, and correct arithmetic and units - A sanity check from an independent angle, such as spend per advertiser compared with Meta's publicly reported revenue - A range around the point estimate and the assumption the answer is most sensitive to ### Follow-up Questions - Which assumption moves your answer most, and how would you measure it with Meta's internal data? - How would the number change if the question meant businesses spending in a given month rather than at any point in the year? - If your goal were to grow this number, which step of your funnel would you work on first, and with what product change?