Lesson 5: Build your own BOTEC
Aim for ~30 minutes. Write your working wherever works for you. Each component has already been practised this week — this is the assembly job. Bring your completed BOTEC to the facilitated session.
Choose one:
Option A: You’re considering donating €500 to an organisation lobbying for a policy change you care about (climate, animal welfare, migration — your choice).
Option B: You’re considering spending 50 hours volunteering for a local advocacy campaign.
Work through each component below. Show your reasoning — that’s what you’ll use in the session.
6.1 Value at stake (Fermi)
If the intervention fully succeeds, what’s the impact? Decompose into 2–3 multiplicative components.
What outcome are you hoping for? (e.g., “policy X gets adopted,” “company Y changes practice”)
Who benefits, and how many?
How significant is the benefit per person/animal affected?
Pick a unit that makes sense (lives improved, animals affected, QALYs, income gained) and estimate the magnitude.
6.2 Probability of success (forecast)
What’s the chance this actually works?
Start with a base rate:
What reference class does this intervention belong to?
What’s the general success rate for interventions in that class? (Look it up or Fermi-estimate it.)
Then adjust:
What factors push the probability up for this specific case?
What factors push it down?
If the causal chain has multiple steps, decompose:
P(step 1) × P(step 2) × P(step 3) = P(overall success)
Give your base rate, your adjusted estimate, and 2–3 sentences of reasoning.
6.3 Calibration check
For each of your two big numbers (value and probability), how confident are you? In one sentence each, describe the range you’d actually bet on.
Value at stake — low estimate to high estimate
Probability — low estimate to high estimate
If either range is wider than a factor of 10 (for value) or 30 percentage points (for probability), that’s honest — note it and keep going.
6.4 Credit share
What fraction of the outcome can you claim?
Organisation’s responsibility:
Who else is working on this? (other organisations, government, market forces, media)
If it succeeds, what percentage would be attributable to your chosen organisation vs background trends and other actors?
Your share of the organisation:
What’s the organisation’s total budget (Option A) or volunteer hours (Option B)?
What fraction does your contribution represent?
Your total credit = organisation’s responsibility × your share of the organisation.
6.5 Years of impact (speed-up / persistence)
How long does the benefit last?
Speed-up: would this change happen eventually anyway? If so, you’re accelerating it by how many years?
Persistence: could the change be reversed? How long before it might revert to baseline?
Coefficient’s default for policy change is 5 years. Does that seem right for your case, or would you adjust it?
6.6 Calculate expected value
Put it all together:
Expected impact = Value × Probability × Credit × Years of impact
Expected impact per € or hour = Expected impact ÷ Cost
Show your calculation.
6.7 The decision
In one paragraph:
Would you act on this BOTEC? Why or why not?
If no, what would you want to know before you would?
Which of your numbers is most load-bearing — i.e., the one where being wrong would change your answer?
This is the question to bring to your partner in the session. They’ll push on your load-bearing number and you’ll push on theirs.