Cost-Benefit Analysis

Cost-benefit analysis is a decision framework that identifies what an option will cost and what it will produce, expresses both sides in the same monetary units, and compares them to say whether the option is worth taking. Pricing the benefit side is what separates it from comparisons that put a money figure only on the costs. It is also written benefit-cost analysis, and the two names describe the same framework. Federal guidance defines benefit-cost analysis as a systematic method of assessing the impacts of government projects, in which benefits and costs are reported using a common measure, usually dollars, to the extent feasible, and are compared (OMB Circular No. A-94, revised November 2023, Appendix A).

The Two Decision Criteria

Net benefits are benefits minus costs. The same guidance defines discounted net benefits as the difference between the discounted present value of benefits and the discounted present value of costs, and calls it the standard criterion for deciding whether a government project can be justified on economic principles, with the highest positive results generally preferred and negative results generally avoided (OMB Circular No. A-94, Section 5.a and Appendix A).

The benefit-cost ratio is the second summary number, the ratio between the discounted present value of benefits and the discounted present value of costs (OMB Circular No. A-94, Appendix A). It sits alongside net benefits rather than in place of them.

The sign convention turns either number into an answer. Net benefits above zero say accept, a ratio above one says accept, and for a single option the two agree, because a ratio above one is another way of saying the benefits are larger than the costs. They part company on ranking, where a small option can carry a high ratio and still add less money than a large one.

Over several years both sides are discounted before they are netted, which is the net present value calculation applied to a benefit stream as well as an outlay, while the payback period answers the separate question of how long the money stays exposed.

A Worked Example

The inputs below are stated for the example rather than drawn from a real project. Everything falls inside a single year, so nothing is discounted.

Costs, year one
  Software license                                 $12,000   stated input
  Implementation and training                       $8,000   stated input
                                                   -------
  Total costs                                      $20,000

Benefits, year one, monetized
  Admin time released    500 hours x $45 per hour  $22,500   stated inputs
  Courier and storage spend ended                   $4,500   stated input
                                                   -------
  Total benefits                                   $27,000

Net benefits           $27,000 - $20,000            $7,000
Benefit-cost ratio     $27,000 / $20,000               1.35

Net benefits are positive and the ratio is above one, so both criteria say accept. Value the released hours at a lower rate and both numbers fall, which is why the benefit side carries most of the argument.

What Enters Each Side

The comparison runs on what changes. Calculation of discounted net benefits should be based on a project’s incremental benefits and costs, so that costs or benefits in the past should typically not count (OMB Circular No. A-94, Section 6.a). That is the relevant-cost boundary already drawn in sunk costs and differential costing, applied to the benefit column as well as the cost column.

Not everything converts. The guidance still expects costs and benefits to be quantified to the extent possible even where assigning monetary values is not feasible (OMB Circular No. A-94, Section 5.a).

Where a Firm Meets It

This is internal decision-support work, so it sits inside managerial accounting rather than in the statements that go to outside readers. A firm runs the comparison on its own choices, such as a practice management platform or a new service line, and again on the advisory side when a client weighs one.

What It Is Confused With

Cost-Effectiveness Analysis

Cost-effectiveness analysis leaves the outcome in its natural unit instead of converting it to money. Federal guidance defines it as a systematic quantitative method for comparing the costs of alternative means of achieving the same stream of benefits or a given objective (OMB Circular No. A-94, Appendix A). Public health shows what a natural unit looks like in practice, where the comparison estimates how much it costs to gain a unit of a health outcome, like a life year gained or a death prevented (CDC POLARIS, Cost-Effectiveness Analysis).

The same guidance treats cost-effectiveness analysis as appropriate whenever it is unnecessary or impractical to consider the dollar value of the benefits provided by the alternatives (OMB Circular No. A-94, Section 5.b). The circular calls it a less comprehensive technique and recommends benefit-cost analysis as the technique to use in a formal economic analysis of government projects (OMB Circular No. A-94, Section 5). So cost-effectiveness analysis ranks options producing the same kind of outcome, while cost-benefit analysis can compare options whose outcomes have nothing in common, because both have been priced first.

Common Questions

Because analysis like this waits behind the compliance work that fills a partner’s week, a trial task puts a block of that recurring work through Accountably’s review chain before your own reviewer depends on it.