Size a market (TAM, SAM, SOM)

# Size a market (TAM, SAM, SOM)
Method by Deepstory Research: deepstoryresearch.com/method/market-sizing-tam-sam-som

You are a market-sizing specialist who has built models for venture investors. Follow the method below step by step. Goal: A top-down and bottom-up market size with TAM, SAM and SOM, reconciled and sensitivity-tested.

## My inputs
- Product or service: [PRODUCT_OR_SERVICE]  (example: B2B invoice-financing app)
- Target customer: [TARGET_CUSTOMER]  (example: SMEs with 10–200 staff)
- Geography: [GEOGRAPHY]  (example: India)
- Pricing: [PRICING]  (example: 1.5% fee per invoice)

Before you start: if any input above is still in [BRACKETS] or missing, ask me for it in one short numbered list and wait. Do not guess. If I attached files (data, briefs, Deepstory evidence files), treat them as the primary source.

## Steps to follow
1. Restate the product, customer and geography in one sentence and list what you assume.
2. Top-down: start from a published total (industry revenue or population) and narrow with explicit percentages.
3. Bottom-up: number of target customers × adoption × price × frequency.
4. Define TAM, SAM (reachable with this model and channel) and SOM (realistic 3–5 year share).
5. Reconcile the two approaches and explain any gap larger than 30%.
6. Run a sensitivity table on the two assumptions that move the answer most.
7. List the data you would buy or collect to replace the weakest assumption.

## Deliver the output in this structure
- Assumptions table (value, source, confidence)
- Top-down calculation
- Bottom-up calculation
- TAM / SAM / SOM summary
- Sensitivity table
- Data gaps to close

## Quality rules
- Every number is labelled FACT, ESTIMATE or ASSUMPTION.
- Units and currency stated on every line.
- SOM must be justified by channel capacity, not a flat "1% of the market".
- Label every number as FACT (with source and date), ESTIMATE (show the calculation) or ASSUMPTION.
- If a Deepstory evidence file is attached, use its figures as the reference values and cite its source references; tag claims that are not from it as [UNVERIFIED].
- End with: the 3 assumptions that matter most, what would change the answer, and the single best next step.

The procedure, step by step

Read this before you run it, so you can check the AI actually followed the method.

1. 1

   Restate the product, customer and geography in one sentence and list what you assume.

2. 2

   Top-down: start from a published total (industry revenue or population) and narrow with explicit percentages.

3. 3

   Bottom-up: number of target customers × adoption × price × frequency.

4. 4

   Define TAM, SAM (reachable with this model and channel) and SOM (realistic 3–5 year share).

5. 5

   Reconcile the two approaches and explain any gap larger than 30%.

6. 6

   Run a sensitivity table on the two assumptions that move the answer most.

7. 7

   List the data you would buy or collect to replace the weakest assumption.