In economics, benefits are the gains in utility, willingness to pay, or welfare that come from consuming a good, taking an action, or adopting a policy.
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Core mechanics
Economists often focus on marginal benefit, which asks how much extra value is created by one more unit of an activity:
$$
MB(q) = \frac{dB(q)}{dq}
$$
In many choice problems, the efficient stopping point is where marginal benefit equals marginal cost.
Private and social benefit
Benefits do not always accrue only to the decision-maker.
- Private benefit: value captured directly by the person choosing.
- External benefit: value created for others.
- Social benefit: private benefit plus external benefit.
This distinction matters because markets can underprovide activities with positive external benefits, such as vaccination, education, or basic research.
Policy context
In cost-benefit analysis, economists compare benefits and costs over time. The key question is not whether a policy has some benefit, but whether discounted social benefits exceed discounted social costs under plausible assumptions.
Knowledge Check
### What is marginal benefit?
- [x] The extra value created by one more unit of an activity
- [ ] The total accounting profit of a firm
- [ ] The legal tax due on a purchase
- [ ] The same thing as average cost
> **Explanation:** Marginal benefit focuses on the gain from a small increase in quantity, not on the total benefit of all units combined.
### When can social benefit exceed private benefit?
- [x] When an action creates positive external benefits for others
- [ ] When markets are perfectly competitive
- [ ] When marginal cost is zero by definition
- [ ] When taxes are regressive
> **Explanation:** External benefits add value that the individual decision-maker may not capture directly.
### Why do economists compare benefits and costs over time?
- [x] Because policies can create streams of gains and losses in different periods
- [ ] Because benefits never occur in the present
- [ ] Because discounting is unrelated to public decisions
- [ ] Because only current-year values matter
> **Explanation:** Many economic projects involve long-lived effects, so timing and discounting matter for evaluation.