How to Calculate Aggregate Benefit in Contingent Valuation
Aggregate benefit in a contingent valuation study equals mean willingness to pay per household times the number of affected households, then set against the project cost.
The Contingent Valuation formula
Calculator
Enter mean willingness to pay, the number of affected households and the cost to get the aggregate benefit.
The average amount the survey implies, not the largest amount anyone accepted.
Everyone who holds the value, including people who will never visit the site.
Measured over the same period as the willingness to pay figure.
Mean willingness to pay times the affected households values the improvement at $10,000,000 over the period you entered.
- Net benefit
- $4,000,000
- Benefit to cost ratio
- 1.67
- Break-even mean willingness to pay
- $15
- Overstatement the result can absorb
- 40%
- Verdict
- Benefits exceed costs
Subtracting the cost leaves $4,000,000, which is the figure a cost benefit test reports.
Every dollar spent buys 1.67 dollars of stated value.
Spreading the cost over the households means the survey only had to reach $15 per household for the project to be worth doing.
Stated amounts usually run above what people really pay, and this one could be 40% too high before the decision flips.
The stated value of the improvement covers its cost, so the study supports going ahead.
How to calculate Contingent Valuation, step by step
- 1Describe the good and the payment. The survey has to spell out what improvement is being bought, how it would be paid for, and by whom. Every answer is contingent on that description, which is where the method gets its name.
- 2Recover the mean willingness to pay. Ask a random sample whether they would vote yes to a stated amount, vary the amount across respondents, and fit the pattern of yes answers to get a mean per household. Use the mean, not the largest amount anyone accepted.
- 3Count the affected households. Decide who holds the value. Drawing the boundary too wide inflates the total, and leaving out households who never visit the site but still want it protected leaves real non-use value at zero.
- 4Multiply to get the aggregate. Aggregate benefit = mean willingness to pay × number of households. Keep the time unit straight, since a yearly amount gives a yearly benefit and a one time amount gives a one time benefit.
- 5Test the number before trusting it. Compare it with cost, then work out the break-even willingness to pay. A scope test, checking whether a larger version of the improvement draws a larger amount, tells you whether the survey measured what it claims.
Worked example: Contingent Valuation
A regulator studies restoring a wetland. The pattern of yes votes in a random sample implies a mean willingness to pay of $25 per household per year. The affected region holds 400,000 households, so the aggregate annual benefit is 400,000 × $25 = $10,000,000 against an annual cost of $6,000,000. Net benefit is $4,000,000 a year and the benefit to cost ratio is 1.67, so the restoration passes. Spreading the cost over the households gives a break-even figure of $6,000,000 ÷ 400,000 = $15, so the survey estimate could be 40 percent too high and the project would still be worth doing. That cushion is worth reporting, because stated amounts usually run above what people hand over once the payment is real.
Contingent Valuation questions
How do survey answers become a single willingness to pay figure?
The usual design gives different respondents different dollar amounts and records only a yes or no, which mimics a referendum and is easier to answer honestly than an open dollar question. The share saying yes falls as the stated amount rises, and fitting that curve recovers a mean per household. Open-ended questions are used less often because they produce more zero answers and more implausibly large ones.
Should willingness to pay be measured yearly or as a one time payment?
Either works as long as the cost side uses the same period. A yearly amount multiplied by households gives an annual benefit, which belongs next to an annual cost. A one time amount gives a single lump, which belongs next to the present value of the project's costs. Mixing the two is the most common arithmetic error on this calculation.
Why report a break-even willingness to pay?
Because the survey number is a statement about hypothetical money, and stated amounts tend to sit above real payments, a pattern known as hypothetical bias. Dividing cost by the number of households shows how far the estimate could fall before the decision changes. A project that passes only when the survey figure is taken at face value is a much weaker result than one that survives a large discount.
Which households count as affected?
Everyone who holds value for the change, which for non-use value can reach well beyond the people living nearby. That is exactly why the boundary matters so much: multiplying a small per household amount by a national population produces enormous totals, so analysts have to defend the region they chose. Some studies show willingness to pay falling with distance from the site and aggregate accordingly.
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