Cost-benefit analysis compares the discounted incremental costs and benefits of alternatives against a defined baseline, including uncertainty and non-monetized effects.
Cost-benefit analysis (CBA) is a structured process for comparing the incremental costs and benefits of alternative decisions against a defined baseline over time. Monetized effects are discounted to present value, while important non-monetized, distributional, and risk effects are reported alongside the numerical result.
CBA can support private investment appraisal or broader social appraisal, but the perspective must be explicit. A cost to one party may be revenue or a transfer to another, and the relevant discount rate and valuation rules depend on the decision framework.
State the problem, required outcome, constraints, decision authority, and criteria for success.
Describe what is expected to happen without the proposal. “Do nothing” may still involve maintenance, deterioration, replacement, or contractual costs.
Compare meaningful options, including scale, timing, design, outsourcing, phasing, and business-as-usual where relevant.
A firm may focus on after-tax incremental cash flow. A social CBA may include effects on households, businesses, government, and the environment.
Include capital, operating, working-capital, implementation, opportunity, residual, and risk effects caused by each option.
Use market evidence or established valuation methods. Record important effects that cannot be credibly monetized.
Convert future effects to present value using a framework-consistent discount rate and consistent real or nominal values.
Calculate NPV or net present social value, benefit-cost ratio, scenarios, sensitivities, and switching values.
Show monetized results, unmonetized effects, distribution, risks, affordability, assumptions, and implementation requirements.
For benefit (B_t), cost (C_t), discount rate (r), and time (t):
For a social appraisal, the net measure may be called net present social value. The label does not remove the need to define whose costs and benefits are included.
A company is evaluating an automation project with:
$300,000 at time 0$150,000 at the end of each of years 1 through 3$20,000 at the end of each of years 1 through 3The three-year present-value annuity factor at 10% is approximately 2.4869.
| Measure | Calculation | Present value |
|---|---|---|
| Gross benefits | $150,000 x 2.4869 | $373,027 |
| Recurring operating costs | $20,000 x 2.4869 | $49,737 |
| Initial implementation cost | At time 0 | $300,000 |
| Total costs | $349,737 | |
| NPV | $373,027 - $349,737 | $23,290 |
| BCR | $373,027 / $349,737 | 1.07 |
The modeled monetized benefits exceed costs, but the margin is small. Benefits could fall by about 6.2% before NPV reaches zero, assuming costs and timing remain unchanged. That switching value makes the fragility of the base case clearer than the positive NPV alone.
A real review would also test implementation delay, adoption, maintenance, cybersecurity, process failure, staff transition, residual value, tax, and working-capital effects.
| Feature | Private financial appraisal | Social cost-benefit analysis |
|---|---|---|
| Perspective | Firm, investor, or specified owner | Society or another defined public perspective |
| Main inputs | Incremental after-tax cash flows | Social costs and benefits, including external effects |
| Prices | Market and contract prices, adjusted as appropriate | May use social or non-market valuation methods |
| Transfers | Cash effect to the firm can matter | Often offset across society, with distribution shown separately |
| Discount rate | Required return consistent with cash-flow risk | Rate prescribed by the applicable public framework |
Results from one perspective should not be relabeled as results from the other.
Some effects may be material but difficult to price credibly, such as:
Analysts should describe magnitude, affected parties, evidence, and direction. Cost-effectiveness analysis may be more appropriate when core benefits cannot be monetized but can be quantified in another unit.
Project sponsors may overstate demand and benefits, understate cost and duration, or ignore correlated risks. A useful uncertainty review includes:
The objective is not to manufacture a single “certain” result but to show how the decision changes.
This article provides general finance and appraisal education, not investment, public-policy, valuation, accounting, tax, or project-selection advice. CBA methods should follow the applicable framework and decision authority.