Why a great team in a small market still fails the fund
Because venture returns run on the power law (Lesson 21 makes this precise), a fund needs its winners to become very large, not just profitable. A brilliant team executing perfectly in a market that tops out at $200m in annual spend cannot become the fund-returner a $150m fund needs, no matter how well they run the business. Market size caps the ceiling before the team ever gets to prove anything.
TAM, SAM, SOM
- TAM (Total Addressable Market): total spend if the company captured 100% of the broadest reasonable market.
- SAM (Serviceable Addressable Market): the slice of TAM the company's actual product and go-to-market can realistically reach.
- SOM (Serviceable Obtainable Market): the slice of SAM the company could realistically capture in the next 3-5 years given competition.
Worked example: a startup selling scheduling software to independent dental practices.
| Layer | Definition | Estimate |
|---|---|---|
| TAM | All practice-management software spend, globally, across all specialties | ~$8bn |
| SAM | Scheduling-specific spend, dental practices, US + UK | ~$650m |
| SOM | Realistic 3-5 year capture given 2 established competitors | ~$60m |
Market timing
The same market can be a bad bet in one year and an excellent one two years later, because market timing, not just market size, determines whether a company can grow fast enough to matter within a fund's life. A shift in regulation, cost of a key input dropping, or a platform (mobile, cloud, now AI models) becoming capable enough to make a product finally work are the classic unlocks worth naming explicitly in a thesis, not left implicit.
Checkpoint
- TAM/SAM/SOM: total market, reachable slice, realistically obtainable slice, narrowing sharply at each layer.
- SOM, not TAM, should drive ownership and check-size math.
- Market timing: why this market, why now, not just why this market in the abstract.
If anything here still feels unclear, ask before moving to Lesson 9.